Any form of user generated backlinks you should step carefully, Google does not want webmasters creating links as this is called manipulate search results. Google loves naturally made back links by the visitors of the site and not the webmasters.
Google over recent years has nerfed links from user generated sites such as:
- Forum Sigature Links
- Forum Profile Links
- Blog Comments in the message field, but even more so in the user name field (big no no).
- Social Book Marking Sites
- Web Directories
- Article Directories
And so on, the list continues to grow, this is because again Google does not want users creating their own links to manipulate search results. Webmasters have been using tools like Scrapbox, Senuke, Sicksubbmiter, GSA and more to make links in the 10's of thousands at a time.
Also when I say nerfed, I mean they have been nuked! and hold little to no value at all... and enough of these links with the right anchor text your find your site ranking very badly for those keywords. Stick to creating great content, use paid traffic like Google Adwords if required (I know its expensive but its viable for a long term strat and good for new sites.)