many backlinks for one url and for one keyword in short timeperiod result as penalty?

Last week I put a single same link (url) with same title in about 25 to 30 bookmarking site. Plus about 15-20 different links with different anchor text and url in 3 different forums.
And now I lost my SERPS position for most of my keywords
I saw this change on Monday morning. Up to sat night all were fine
Is google updates on Sunday afternoon or Am I penalized??
Or google has changed its algo for serps
What should I do now?
Can targeting one particular product or url or anchor text is not good strategy?
Thanks

 

How badly were ranking effected?

In my experience a site with very few pages doesn't suffer from the over-optimisation on one page penalty but sites with 50+ pages and only one page having a decent amount of inbound links does have a risk.

I would always recommend you vary your anchor text with prefixes and suffixes to make it look more varied.