Looks well thought out - I think the idea has great potential! Just a few points on the marketing pages: * Why do the Twitter / Yahoo / Digg links on the home page actually link to those sites? Maybe it's because the arrow pointing up to the T for Twitter, but I clicked one of those links expecting more information about how your service integrates with that site. Instead was swept off your site. I'd gander that most…
I also clicked on a logo, expecting it to change the picture beneath it. Completely agree, audience already knows about these sites, and besides, the UI suggests it's going to switch the picture.