If I were on the bike trail, training or whatever (especially on a weekend), I'd probably agree. But during commute hours when dealing with traffic? I think not-- it's akin to tailgating. In unpredictable traffic, everybody needs room to dodge and brake. I don't want anybody drafting me on my way to or from work on city streets. And likewise, if somebody ahead of me needs to hit the brakes because of a stupid cager, I don't want to be eating his rear wheel.