Not sure I agree with this. My startup (Frogmetrics, YC S07) hasn't tried to sound big or small. Our site focuses on the service we provide, in concrete language with a clean design. We don't try to sound bigger than we are, but we also don't play up our smallness with a bunch of cute catchphrases either. We've been pretty successful so far at getting big customers, and I think we'd have done less well with a more "startup authentic" aesthetic.

I think the better lesson is to tailor your messaging to your target buyer. If you're selling to a level III coder at a big company, put the message in a form (s)he will like.