This card suffers from the "50th card" syndrome. That is, it's the kind of card you really wish you could put into your deck...but that would mean taking something better out.
At the moment, the greatest benefit of Foxfire is econ denial for drip economies. With a trace of 7, you're basically guaranteed to burn away their Dyson Mem Chips or Access to Globalsec, hopefully deactivating their Underworld Contacts, or destroying one of their Data Folding for a similar effect. These cards are definitely seeing play alongside The Supplier. I expect to see more in the near future, as Off-Campus Apartment speeds up the setup time for UC-based decks, and people experiment with the Criminal cloud suite (Spike et. al)
There are other things Foxfire can be used for as well. If the runner doesn't immediately use one of their Shards, you can remove those. We've seen at least one moderately successful build using Woman in the Red Dress; if something like that is floating around your meta, you might consider this card. Stealth is still pretty common, and Ghost Runner is a valid target, although it might not be worth the click to trash it, even for free. And the Anarch deep-dig archetype sometimes relies heavily on Virus Breeding Ground, which can be removed with the Fox.
But by the time you slot in your agendas, your ICE, and your economy, most decks only have an extremely limited number of slots left for utility cards and counter-plays. These are usually the most competitive slots, because these are the cards that give your deck the most personality and uniqueness. Do you run IT Department, or Corporate Troubleshooter? Hostile Infrastructure or Psychic Field? These cards are the connective tissue that makes your pile of cards into a cohesive game plan.
And Foxfire...just doesn't fit any of that. It's annoying to certain runners, in some matchups. Is it worth putting in just for that? Over, say, Cyberdex Virus Suite, which is similarly situational but utterly crippling to the runner when it matters most? At the moment, the top two decks on NRDB which use Foxfire are joke/theme decks, so the general consensus seems to be "no".
Perhaps, in a future set, some virtual resource will get released that some corps just cannot deal with any other way. Maybe there will be some uber-link card that gives the runner something like 3 with a single link. If something like that happens, I could see Foxfire coming back. Until then, though, it will sit lonely in the binder alongside Bad Times and Freelancer.