My current setup on my messageboard is that I do not allow guests/unregistered members to view profiles....so this includes search engine spiders. I see all the spiders trying to crawl to my members' profiles, but they get stopped with error messages since guests aren't allowed to access it. I did an rel=no follow to the profiles, but I figured I didn't want the spiders spending a lot of time crawling profiles which I felt was useless information to crawl. Am I shooting myself in the foot by doing this? Will the error messages the spiders see have a negative impact?
Nope not at all. You can also block them using the robots.txt file Give this command in the robots file Disallow: /yourfiledirectory/
The good part is you dont waste crawl budget and cut down the number of links per thread to non-content rich pages. The bad part is members may want their profile indexed with PR. You really only want your valuable content recieving the Google attention. Its also a good idea to block your calendar.php as its also 1,000s of pages of duplicate junk.
Yes, I blocked calendar, and have been blocking profiles but was debating on letting spiders crawl members' profiles but with a no-follow tag on profiles.