I suppose. Certainly not 'and have it just work', but I'm really skeptical that many web apps have such complex api dependencies that you couldn't just fudge a

I suppose. Certainly not 'and have it just work', but I'm really skeptical that many web apps have such complex api dependencies that you couldn't just fudge a new one in. Even app-engine apps have been successfully run using an isolated stack. ...and certainly most 3rd party APIs really wouldn't care; just another end user. Nothing special.