Stumble, delicious and I guess also digg links are nofollow. I guess Google dont bother so much about that links Social networking is just about traffic, and not for climbing SERP. Just my 2 cents.
What if I spam my competitors URL in Digg exchange requests / Stumble requests / Link selling and just pretend it's my own? Google thinks about this as well, so throwing a penalty won't be this easy, at least it shouldn't be because it's not completely fair.
I dont see how it would really be fair, just because you do well on Stumble makes no real difference to your serps for search engines simpley helps your site get advertised on the Stumble network, if the site is not the right type of site for stumble it done matter how much you spam the freebie section doing stumble exchanges you wont do well in Stumble. The more votes you get for your site the more it will get seen by other users, if the site is bad they will vote against it, they will be voting against your site much quicker than you can do stumble exchanges I get alot of visitors of Stumble from the right pages, but if you post a page which does not intrest Stumble users no matter how much you try to cheat the system it just does not work, there are to many other people out there voting. Unfortunatly I have to agree with the last post though who says Google is fair I think they are getting way out of control infact and seen a post on this forum which I thought was not far from the mark. http://forums.digitalpoint.com/showthread.php?t=618394
well, my sig. contain link to my site, i dont see any bad effect just dont spam the link, then its ok
Hell will freeze over before I post links to my sites here - they rank well and I would like to keep it that way...........