This news is a little dated now as Matt Cutts reported on it in mid-December, but I felt it was worth sharing for those who have not yet seen it.
It seems that now, it is official that Google does use Twitter and Facebook links as a ranking signal for organic results.
Google takes into consideration the reputation of the author on twitter and Facebook to help determine if the link posted is relevant and of value. If it is, it can contribute to your organic search rankings.
This does not mean you should go out and create dozens of phoney Twitter and Facebook accounts – those spam accounts won’t help you much as they will have no history, and no real followers or authority.
It is also important to note that these links are used very lightly and do not play a significant role, however, you never know what the future will bring.
Here is the Video.