If I have YouTube videos that link to my site, this might lead to penalization? And what about Yahoo and Facebook? I get traffic from all of the 3, Youtube- my videos, Yahoo- my site is popping in discussions, Facebook- site page of course. Maybe Google doesn't like this? Yeah that sounds a bit dumb when I think this through, but I'm a September 4TH victim,still crashed, still have no clue why.
If anything YouTube should help. YouTube is owned by Google, so I think that they may have some bias for the ranking of videos. I always seem to see 1-2 videos ranking on page 1 of my niche. Yahoo and Facebook are legitimate websites, so I wouldn't think that Google would consider them spam.
Google may not consider Yahoo and Facebook spam, but they do consider Yahoo and Facebook to be competitors. Google does what is best for Google and it wouldn't be surprising if they favor their own things in results like Youtube (which they own).
It depends on how many links you have from the social networks you mentioned, what anchor texts you use and whether those posts are public (can be indexed by Google). Anyhow, if you get traffic from them, that's a good thing and maybe I wouldn't worry too much about the search ranking, unless it has been getting you decent traffic too.