The key to this card is its type.
By virtue of being an Upgrade, and not your usual economy Asset, Shell Corporation allows near-infinite options. You can install it in the root of a Central server, for example the Archives full of Shock! or Shi.Kyū, or maybe in a Remote server, together with an Ambush-type Asset.
It can become almost permanent, if such a thing is even possible for Corp cards, because a Runner will hardly go on a server with an unknown card advanced a few times, especially if he has reasons to believe it could lead to a flatline or to other dangers.
In tag n bag you might wanna install it with Ghost Branch. If they wanna trash Shell Corporation they will have to take a few Tags. In an Haas-Bioroid you might go for Cerebral Overwriter or Aggressive Secretary. The first works anytime, the latter might be more useful in late game.
Shell Corporation is not a card that's useful absolutely, but it's a wonderful card because it's the first of its kind and offers an entirely new kind of mind game. In Jinteki it obviously shines, given how they have most of the dangerous cards and can make even Archives a nightmarish server to thread upon.
In the other Corps it might take some working around it, but it can be a valid economic option. It can also become sort of a protection from the all-time-dreaded Account Siphon. It works exactly like Kati Jones after all, so if you charge some credits on it, you can take them back after a Siphon.