My experience with PR 0 / (N/A) profile backlinks
The results have been that eventually I seem to get some power with them just by the sheer number of them, but it takes a LONG time. This actually caused me to give up for a while then when I would check my sites for kicks my rankings were slowly going up and I ended up with a couple hundred bucks at the end of the year which motivated me to pump out about 15 more sites with the same process.
So I suppose in my experience, they will have an affect (mind you these are micro niche's) but it will take a lot of them and possibly a very long time.
I've sinced moved to article marketing and I've seen a tripling of my Amazon clickthru's in 1 month. So this is seeming to be effective but at the same time I'd like to have them getting organic traffic for their search terms that they're built around.
Just sharing some info on my experience with these profiles. It seems like it may be worth it to just find/buy some high PR links and do less rather than be cheap and mass post low power links