Those numbers being off just by a factor of "only" 10-50X (which I think is reasonable given Compete's record) would make a big difference for a B2B site. Even

Those numbers being off just by a factor of "only" 10-50X (which I think is reasonable given Compete's record) would make a big difference for a B2B site. Even more important from the perspective of a startup would be the presence of an upward trend - and with Compete, I've seen their estimate for our traffic fall by over 50% in months where we grew by around 40%. I'm pretty sure for a "decent sample" - at least, accurate enough for the data to be useful for anything - you need to be at least a top 100 site, and even then I've heard stuff from a couple webmasters of those sites that Compete data is off by an order of magnitude or so.