I think twitter isn't looking for an admin assistant but a really smart would-be entrepreneur with most of the capabilities that the founders posses but at a lower level. Hence ready to do some leg work or dont-know-value-add-yet work which the founders aren't sure of spending their time. This is a great opportunity to tune ones self, better than joining twitter as a developer, marketer or anything else.
The most you get out of any job depends on whom you work with and how much you extend your profile.
1. What better than direct interactions with the founders. I can imagine one stopping to read all these pep material around startups as you a have a real people telling you their tales first hand on and off.
2. This can very well be what Marissa Meyer did for the Google founders to save their time.
Unfortunately I am in India!