I'm here with a new issue regarding Stumbleupon a social networking website. As you all know that nowadays social networking/bookmarking websites play a vital role in sending one links to your site. But here I wanna ask you all is stumbleupon links comes under spamming or not.

I'm a webmaster of a site having PR-4 and good keyword positions over the search engines. A day ago I've tagged a link on stumbleupon of my website, certainly I've seen that over 1000 visits drawn to that page. Okay that was good, but very next day when I was in a process of analyzing my web-ranking, I was shocked to see a major flactuation has occured on more than 3 keywords on Google. A big jump from 22 to 86 place for a a keyword and some minor flactuations could be seen but only on Google. My question is that whether tagging or bookmarking with stumbleupon can cause demolishing in ranking or in other words either google consider pages tagged with SU (stumbleupon) as spam. What do you say it about? Any body who can satisfy me with regards to it.

Thanks

Bilal