The problem with your freemium model is that there's no real incentive to jump up once you're over 50MM impressions.  At over 50MM impressions, you have your own in-house ad sales force (or you should) and they can open the kimono to media buyers.  I think they're kind of screwed in that they have to charge everyone and I can see the logic that a min/max model would spit out $5,000 as the magic number.  Plus, the only people who care about impressions are people selling on a CPM (or similar) basis.  Someone like, say, Dropbox or 37signals or even Consumer Reports doesn't care.<p>(Lastly, you've been around here long enough to know not to sign your comments/posts.  If you're going to add extra stuff to the bottom, add some of that sweet, sweet LA sunshine.)