Originally Posted by same time
The direct answer to your question: No.
It doesn't physically slow the lead rider down, but since he has been tactically neutralized, he will probably give up and rejoin the pack.
It doesn't always work, though - early on in the 1995 Tour De France, Miguel Indurain broke away on a flat stage, and an ONCE domestique went out to "drag him back". Indurain didn't give up, and dragged the guy something like 50 kilometers to the finish. Indurain was beaten in the sprint, but he gained some time and mentally deflated his rivals back in the pack.
That was Johan Bruneel (sp) the Discovery team dude, right? I really thought is was lame for him to do that, but that's racin'.