StumbleUpon, the video referral site where registered users recommend videos to others, has grown to 5 million registered users who "stumble." or recommend, some 350 million Web pages per month, Garrett Camp, co-founder, told Beet.TV in this interview. The San Francisco-based was purchased by eBay last year, but operates independently. The company recently expanded the video sharing sites it curates. The company hopes to add Blip.tv soon, Garrett told us. I just spoke with Blip.tv CEO Mike Hudack who told me he is quite enthusiastic about the prospect.Garrett shares his vision for the emergence of contextual video advertising on the site. And, he gives some good pointers for producers on how to make videos more likely to be shared or "stumbled." Check this out.-- Andy PlesserDisclaimer: Blip.tv is the primary video sharing site of Beet.TV and Blip.tv sells and serves advertising into our clips. Posted on Beet.TV on Saturday, June 14, 2008http://www.beet.tv/2008/06/ebays-stumbleup.html Less