[greglindahl]

At blekko, we did not find this issue to be a significant one... almost everyone who banned our crawler was a crappy over-SEOed website.

[AznHisoka]

https://www.linkedin.com/robots.txt

https://yelp.com/robots.txt

There goes all Linkedin + Yelp content from your index.

[betolink]

What about https://www.facebook.com/robots.txt

..and medium-sized/small sites are even worse.

The irony of Facebook being a core part of all NSA surveillance programs and their terms of service including their "Automated Data Collection Terms" https://www.facebook.com/apps/site_scraping_tos_terms.php

[greglindahl]

If you surf LinkedIn logged out, you'll see that there isn't very much information available anyway. And there's no money in people search.

Yelp was very responsive when blekko wrote them; as you can see ScoutJet has the same access as googlebot.