When I saw the vid, I just realized I've been pronouncing "Posterous" wrong all this time. I assumed it was long o, as in "post". But to hear them pronounce it, it rhymes with preposterous. My way seems better to me, but what do I know.
If anyone tries to correct you on the pronunciation maybe you can tell them:
"Post-erous, posterous, smackerous... They're too busy putting in new features to care about stuff like that. They care about results, not pronunciations. That's the start-up way."
(Unless of course it's Garry Tan trying to correct you on it.)