Planet13 - 4:42 pm on Jan 22, 2012 (gmt 0)
To add on to martinibuster's excellent post:
4) If it WERE that cheap and easy, your competitors would do the same thing, thus negating any benefit you would get.
One other thing about this:
We tend to look at the top ranking sites and try to copy what they do.
Instead, maybe we need to look at the sites that rank below us and AVOID doing what they do (if no sites rank below yours, then look at sites that can't crack, say, rank page 4 and below).
I would assume if you were to check the backlinks of sites that rank Page 4 and below you will see lots of them with forum profile backlinks, too.