I'm not convinced of that. Sure, you can create an argument for the point that sounds good, but that doesn't mean it's actually true.
What I think that really does is get the person doing the hiring off the hook. If you hire a dud from MIT you'll get less flak for it than if you hired a dud from an unknown school. (Or someone without a degree.) It's the same idea as "No one gets fired for buying from IBM."
What matters is proving what you've done and can do.
We will take a hardcore guy who never even went to high school who codes open source projects or has built great things over a CS guy from Stanford but has never coded production code in his life, no question.
I think anyone who says they are looking for 'top CS schools' would agree. Except Google. They really want those degrees, go figure.
b) Joining Posterous is actually a cool way to avoid bad culture because you'd have a key hand in creating the what the culture would become. Say if you joined us at Posterous -- it would be you, me and Sachin, making great software and building a great company.
So, how about it? =)
However, if you can prove strong or exceptional skill and achievement in whatever you have done tech related, I am sure it won't matter if you went to an elite school or not (and if it does, you probably won't like it there anyway).
For most businesses (startups in particular) that do not have the time or resources to filter candidates, an elite school is a general simple quality filter, but the world is full of examples of people who did not go to school let alone an elite school, from Richard Branson to Dyson to Jobs to the mass of not-so-famous.
Worry not, shine and hopefully you will be noticed.