What is the value of a dofollow link in a profile for a web 2.0 site or forum? If there are thousands of links going out of these sites from everyone's profile, doesn't it lower the "power" of the links? Is it still worth the time to make a profile / add links? (example: PR 5 site that has dofollow profile links - http://community.guinnessworldrecords.com/)
If there are thousands of outbound links on the person's profile, then yes, the juice it passes along is diminished. However, since pr is assigned to an individuual PAGE and not a website as a whole, I think you'll be hard pressed to find many (if any) profile pages that have PR. so, while you still might benifit from gaining a backlink, you're not gaining the juice you would from a backlink on a page that has much (if any) pr.
No, in my profile it has no rel. So 1 person says they have almost no juice and another says they have quite a bit..
The cold, hard truth is that the vast majority of profile links pass a miniscule amount of link juice, if any at all. You'll find some high PR profiles - those are the ones with backlinks, rather than the "create and forget" type ones that most people tend to do. Unless you spend a lot of time and energy optimising the page that contains your link, then you will get nothing or close to nothing from it. Creating 50 profile pages then doing nothing is a complete waste of time. Creating 50 profile pages then having to optimise each one takes a lot of time and effort.
Stop thinking that google know everything. They are spending much more time trying to figure a way to stay on top of the SE race and to stop the scammer. Profile links if done right is considered only blue/gray hat. Unless you create 10,000 links for a 7 days website I don't think google will find out about it. Just remember that Google try to classify websites by theme. If your link is in a website that talks about soccer and your anchor text is about anxiety and depression google algorithm might find odd and flag it for future observation by a human.
It's still spam if you're doing it for the sole purpose of joining a forum for the link. If you're going to sign up at least contribute something of value to the forum you joined. (Note: I am not talking about anyone in particular here on this forum. It's just a broad and general statement.)
if it's dofollow and you can get anchored link, for me it's good. If you want perfect link, just buy it.
To get max 'power' from profiles links you should link your profiles from other sources (not necessarily quality ones