martinibuster - 10:27 am on Feb 19, 2010 (gmt 0)
I agree it can be useful in the way you just described it. That actually is the way I recommend it be done, if you're going to do it. I wrote a post about doing it in that manner about a year and a half ago. Non Spammy Link Dev Using Forums and Blogs [webmasterworld.com]
It requires a significant commitment of time, generosity with information and a genuine participation in the community that allows signature links. It's not a scalable link development strategy because it requires time and authenticity.