It's also apparently bad form to get one's resume to an employer twice (probably due to deciding which agency's fee to pay, or none, if you sent it in directly), so try to avoid doing that.

Yeah, one of my mates was involved in recruiting developers for a while and they always had to discard potential recruits if they had got their detail from two different agencies, however good the recruit was. They had got embroiled in expensive legal fights in the past, with agencies sueing then for fees when they took someone who was also referred by another agency. Crazy.