phranque - 1:27 am on Mar 29, 2013 (gmt 0)
You MUST include a blank line after each record, i.e. before the next User-agent.
that's true according to the robots exclusion protocol.
you may not have blank lines in a record, as they are used to delimit multiple records.
however according to the (non-standard) google documentation...
Note the optional use of white-space (an empty line) to improve readability.
as jimbeetle says:
That's great for Google, what about other bots?
given that the only bots that have a chance of honoring your robots.txt are non-google, you might want to add the blank lines between groups.