Do links in forums increase PR?

Yes they do.
Wanna get a sig. link from me?

 

Yes they certainly are counted as backlinks!!

 

Damn RIchie,

8k posts! Your sig is worth a lot of $$$

 

Yes posting in forums with your signatures are good for everything

You get traffic
you get backlinks
you increase your chances of a good PR ( if the foum is having a good PR)

Last but not the least you always learn some thing

 

They do, unless the forum owner has prevented it.

 

but dont forget few forums use nofollow.

Also many backlinks from forums are not counted by google after the page has been archivved

 

If they arent nofollow and are indexed with PR they should

 

Are there any negatives for posting your sig link in forums ?

 

There should not be any, assuming it's a quality forum. If you are posting in forums that are full of spam and crap content, then those links may be discounted...

However, posting in a respected forum should only bring in bright blessings. Not only should it effect PR and SERPs to a certain degree, but it also will pull in quality (and relevant) traffic. (Sigs have a better CTR then forum ads)

 

Of course, especially in top forum sites, like DP.

 

Of course links in forums help in link building

 

Ye as said before they do, and can heavily impact it. Althought alot of sites forbid it, but just read rules first and if there's nothing against it then put in ur sig.