I had a few sites that I occassionally socially bookmarked at social monkee. Well 2 of those sites were killed by Penguin. I build all my sites the same way and obtain white hat links…I never spam. But I tried social monkee and took a big hit.
I am seeing referring sites in Google Webmaster Tools like
I signed up for social monkee but never actually used it, I decided I didn’t like the sound of it, it didn’t seem like I would have any control over what they were doing.
But I have many links from strange sites that I have never visited, e.g. howdoi-getpregnant.com and howtogetyour-exgirlfriendback.com and have no idea why they are linking to my site. Social monkee may have been the cause in your case but equally it may not.
I used Social Monkee a little bit and saw no negative effects from it and it seems that the links are still active. I think the problem comes if you use it too much and don’t vary the anchor and descriptions.
Social Monkee uses spammy bookmarking sites that would be easy for Google to detect.
…also, FYI: Penguin actively penalizes sites that Google believes engaged in link spam. This is new. Until now, Google generally took away ill-gotten link authority and penalized sites that were selling links. The big G rarely punished sites for acquiring spam links.
Sometimes spammy sites fishing for trackback links to sites. I also see strange pages link to completly new sites in my gwt, where it makes no sense to link to.