I think I disagree a bit with the efficiency evaluation made by Diogene. While it is true that "clicking for 2 creds instead of 1 is very good," I feel like once you factor in the click and card it takes to install this, it becomes not very efficient, unless the game goes pretty long. First of all, let's consider Hedge Fund. It costs a click and a card to net 4 credits, pricing cards and clicks roughly at 2 credits each. Of course, since Hedge Fund is one of the better cards in netrunner, 1.5 to 1.75 credits per click or card is a probably decent baseline for the efficiency we want out of our cards/clicks. Even cards with flexibility like Predictive Planogram have a 1.5credits/click or card efficiency rate.

Now let's consider Nanoetching Matrix.

Base Efficiency:

Immediately we see that the efficiency is never going to outdo Hedge Fund, since it at most generates two credits per click, which is the rate of Hedge Fund. That's fine, since most cards don't outdo Hedge Fund. However, the main problem is the steep initial cost of a click and a card to install, before we start getting hedge fund level of efficiency out of it. After 2 uses, it generates 4 credits for 3 clicks and a card, which is basic-action level efficiency, something we really want to avoid. At 4 uses you got 8 credits for 5 clicks and a card. Roughly 1.333credits/click or card. At 6 uses you finally got 12 credits for 7 clicks and a card, or 1.5credits/click or card, which is more or less the baseline efficiency of most standard playable netrunner econ cards. It takes 6 turns to get to the minimum efficiency for it to be really considered, and more turns than that if you aren't using the ability every turn it is installed. The problem with this is that if this is drawn anytime past midgame it's much worse than the standard economy cards. If it's drawn relatively early, then it still can only approach the efficiency of hedge fund. The risk-reward of the card just doesn't seem to average out to something worth including.

Advantages/Disadvantages:

As Diogenes pointed out, being an asset that is almost never worth trashing has it's advantages. For one, it can bait out a run from the runner, upping it's efficiency that way. You can Divert Power this since it's almost always going to be on the board once you put it there. You can trigger NEH or other "install" benefits. But it also has some weaknesses that operation based economy cards don't have. It makes centrals slightly weaker as a trashable card, and the lack of burst econ makes it harder to recover quickly, which can lead to more losses in efficiency elsewhere. Most drip econ is more efficient than even Hedge Fund, like Marilyn Campaign for corps or Daily Casts for runners. This is to counteract the bonus efficiency that burst econ can bring (since you can install more cards, earlier, which can generate more money), and for when they are drawn 1-3 turns before the game ends.

As I see it, I don't think the card will see much play outside of Divert Power decks that value an asset not worth trashing, and MirrorMorph: Endless Iteration decks which can make use of the unique click cost to fire the ID more consistently. It's not a card that has lots of raw economic power/efficiency, and so I don't think it will be widely included in HB decks as an econ engine. Rather, I think it finds it's home as a card which makes up for it's lack of efficiency by providing synergy with Divert Power or ID's like MirrorMorph.

The Anarch's version of Criminal's Docklands Pass, providing multi-access into R&D instead of HQ. While Docklands Pass is a card that sees it's fair share of standard play, eXer sees very little play, and probably for good reason. It costs an additional MU compared to Docklands Pass, and can often be incidentally trashed by the hyper-popular suite of Cyberdex Sandbox, Cyberdex Virus Suite, and Macrophage that is dominating the meta as a natural counter to Hivemind MaxX. Even if the Corp isn't running the anti-virus suite, spending 3 clicks to trash what the runner invested 2 credits, a click, and a card into isn't a horrible trade for the Corp, which should immediately raise some warning signs about this card.

However, this does do one important thing for the Anarch faction. It provides multi-access. R&D has always been Shaper's server to attack, while HQ is constantly terrorized by Criminals. Anarchs got... what? Archives? For Anarch decks that can't spare the influence for Conduit, eXer is a cheap, rip-off replacement, but one that can still get the job done. Multi-access is just so valuable to a runner, since it's almost like providing another run, free of clicks, and a free pass through all the ice. Chances of finding agendas double, trashing combo pieces with Imp is more likely, so on and so forth. It may be the case that the Anarch, who's strengths lie elsewhere, may actually appreciate an odd out-of-faction effect that helps shore up some of it's weaknesses, even if somewhat shabbily so.

Sadaka, like many traps, don't act like normal ice, but instead function as a weird kind of operation that fires when the runner runs on it. Since it doesn't end the run, it won't protect any servers, and it trashes itself so it's a one-time use, just like an operation.

The only key difference between Sadaka and an operation that has the subroutines in it's text box is consistency. Operations you play are resolved immediately, whereas Sadaka requires the runner to run on the server in order for it to trigger.

If you start to analyze the efficiency, you'll realize it's actually really darn good. This costs 2 credits, a card, and a click. First sub gives you back a card, while the second sub has you discard a card to trash a card from the runner. The first sub makes Sadaka card neutral. So where did our click, two credits, and an HQ trash go? Well, it went into trashing one of the runner's resources! Suppose you trash a daily casts with 6 credits on it using Sadaka. Then you've essentially traded a card and a click for 4 credits. That's the same efficiency as hedge fund! (Of course, this is assuming a few things like runner credits/clicks/cards are of equal value to your own, which probably isn't entirely true). Trash anything larger like The Artist, Professional Contacts, Red Team, Liberated Account, or Assimilator and you're coming out on top by a ridiculous margin. While this doesn't seem that likely, keep in mind that you get to choose which resource to trash, and the runner will likely build up quite a few resources (Assuming they aren't going tag me). All this doesn't consider the additional value you get from this being a facedown ice that has bluffing value, and might eat the expose of a Deuces Wild, something Hedge Fund never could've done.

I think the best way to think about Sadaka The efficiency of this card is nuts, it just needs you to be able to get the runner to actually run the ice decently soon. In a sense, it's like you are investing a card and a click to give you higher returns, but significantly later. It's like if hedge fund read "Net 6 credits after 2 turns." I'm not sure if that's better than the current hedge fund, since it means you recover slower and there is a window of weakness where you've invested without return. If you think you can get the runner to run Sadaka consistently and soon, this could be a valuable include - albeit as an funky value operation, not a piece of ice. Something like Jinteki: Restoring Humanity could be a good home for this card, allowing you to put it on archives which will likely be ran.