Getting backlinks from forum signatures is in existence from the day forums came into existence and had the feature to have backlinks. Is it still a good strategy I fear no. Forums are meant for quality discussions getting solutions for problems that you cannot find anywhere else in internet. Using such a wonderful resource for the same of spamming the search engines for backlinks is not a good idea.
I am personally not against it but if you see forums like digital point forums they allow forum signatures in exchange for minimum amount of postings and this actually helps the spammers more. I have seen many just start useless repeat threads or one do one line posts just to create an extra page with backlink. Digital point forum is a typical example of forum spamming most people who visit there are lacking of any SEO knowledge and this leads them to wrong assumptions on forum signatures.
There are discussions here just to know what keyword to use in forum signature, which page to link to, whether multiple pages from same sites can be linked, Is text required besides anchor text etc. I feel all these are just waste of time people can rather spend their time usefully than spamming forums for signature links. I request leave the forums alone they are very useful places for getting quality information.