[vanilla_nut]

I understand the risks you're talking about here, but it's not like OP will start working at Google and suddenly his technical skills will atrophy. It is still a very competitive place to get into and a place where great work takes place. Even if OP doesn't get extremely interesting projects, a more established company is often better in terms of mentorship. Not to mention the fact that financial stability as well as the job security of working at such a large company have their own benefits.

I think OP could work at Google and have a promising career start, while taking on the risk of working on slightly-less-interesting projects.

At the same time, OP could work at this startup and make a bucketload of money through equity while working on fascinating projects. But the work could also be boring API stitching. Or the hours could be really long, and OP might have no outside life.

They're both good options. But back to the point I was originally trying to make: it's not like OP is going to work at Google and then never get hired by a startup again. In fact, working at Google is such a positive signal on a resume that it might actually make it easier to work at startups in the future.