phranque - 7:47 am on Jun 9, 2013 (gmt 0)
the snippet user agent is used for urls shared on Google+ and it isn't a bot.
google calls it a "fetcher" which is an appropriate description.
This service is different than the Googlebot that crawls and indexes your site. These requests do not honor robots.txt or other crawl mechanisms because this is a user-initiated request.