Its highly genuine method to get back links
Its used in signature space etc
SEO Expert here. They can still be useful if you fully populate the profile with relevant information and LOTS of it! 300 words or more isn't seen as "profile spam" by Google. I published a large case study on this on my review site for Sick Submitter: www.profilebacklinks.net
And as mentioned by others above, the Page Rank (authority) of the site the profile sits on plays a large roll in the effect the link will have on SEO.
Profile link is not counted as a good quality back link in Google, They had already told that profile link is counted as a web spam and it affects in Google penguin update. previously profile link is counted as a back link but today's Google updates don't allow this. so build good quality link, best way to make guest blogging.
No there is still allot of significance, to having good quality profile page links i no this for a fact. How? because I been posting my website called Web TV And when i first stated my Alexa traffic rank was at 250000000 now its at 40000000 in just 1 week.
Profile back links are one of the ways by which you can link back to your site. It involves adding your website URLs to the personal, professional, or business profiles that you create on various websites. You can sign up as a user or member on forums, social media sites, and other kinds of membership sites. Many such sites allow you to include your website URL on your profile, as well as insert links into your signature, comments, or updates.
Backlink profiles are commonly discussed in SEO forums as if they mean something. In most cases the backlink profiles that people build are completely useless. As I recently explained in one SEO forum, “numbers of backlinks has nothing to do with search engine optimization”. You don’t optimize a Web site through backlinks.