I don't think so profiles backlinks is effective after the last panda update. Because I have created micro niche site. Site is 6 month old. Not too much competition. I created more than 50000 profiles backlinks many of them not public viewable profiles. But Don't you say every one profile need to login to check it. I read same where on the forum that google index non public view able profiles. I have also lindexed account. Daily I indexed 6000 Profiles and lindexed report says my crawls success rate is now 95 %. But my position on google is 76. Before profiles backlinks it was the same position. May be little changes. My competitors sits backlinks is not more than 3000. Google index only 150. I saw many domains are page ranked domain. One day i saw google index 4000. But after two days everything is disappear. My site is not sandbox and now position is 26. I am worried to see position on 26 keyword i didn't give any profile backlink to this page. And the article on this page was just pointing something to the other resources. Nothing else. This article is not more than 100 keywords only links to the other orignal product. And just my main keyword is only in the title and this keyword take positon in serps on 26. And this is my main keyword on this page. If i will do some comment backlinks may be i will get position in google top ten.
My thoughts:
Profiles are harder to get reuslts with Post Panda but it is still possible to get good results with profiles in moderation, 50k is probably going to be counter productive.
There is a strong correlation between over use of profiles and low quality sites. You say you are running "micro niche", those are also harder to work with these days. I still have lots of micro sites making money, but I am no longer building them.
Panda was more about content than it was about backlinks. Mass linking poor quality sites doesnt work too well. Try smaller numbers of profiles on better quality sites and you may fare better.
Ref comment backlinks... same applies... unless they are high pr do follow on moderated sites with low OBL, those links are good... but most blog comments are junk, certainly scrapebox links are going to be junk.
The best result I had post panda with profiles was on an aged site, decent amount of genuinely good content... stuff people actually read. It was PR4 and had been for some time... starting dripping profiles out at a sensible rate and moved it from #20 to #6 on the desired term.
I have another site also established which I sent large numbers to, similar to your own experimeint, and like you got nowhere.
Key is to have decent sites, some decent links, lots of variety and use profiles / aa comments as one ingredient in the mix. You will NEVER rank a site just using profiles or comments, but they can help you along in certain situations.
