It seems that in Stumble trades, people always want to be befriended. What is so important about that?
StumbleUpon is a website where you can share the website that you like , base on your interest . They have now more than 4 miliion users , so it a great website to get traffic to your blog/website cause they have so many users ... http://youtube.com/watch?v=Z9fvlVCLh2c&feature=related See the video above for more info .
Some think it is one of the ways you get more effect from your stumbles. It's supposed to work best if you have a lot of friends and fans. No one knows if it really works; it's just one of the theories about how SU works.
STumbleUpon itself is a stupid site that gives some people impression that there site get's some traffic (useless as it convert's very bad)
they thinkmore friends in SU mean more traffic but they should realize that traffic from SU sucks. its never convert at all.