I've noticed this on 3 occasions now and I must admit, I've found it quite strange, rude....
On a lunchtime ride on my fixed I rode past some fella with all the kit on with his flash looking road bike, overtook him with plenty of space, said a quick hello and carried on, after a couple of km's I turn around to find him sitting on my wheel.
Commuting back on my cross bike again, overtook some chap, quite a quick pass as I caught up with him quite quickly, again, find he's sitting on my wheel, even when I pulled to one side to indicate I wasn't happy with him sitting on my wheel (accompanined with a hand gesture waving him through, he again moved over and sat on my wheel.
And then yesterday, boot on the other foot, been out for a decent length ride with a mate, just left him and on my last climb home and I can see a roadie coming up at quite a pace, knew he'd catch me as I was taking it easy. Yep, caught me up after a minute or so and again sat on my wheel, even though before he was going quite a pace, he should have passed me without problem.
What's all that about?
Okay, when I'm riding with a group we draft, I've even got chatting to someone I've met and ended up riding together, but I wouldn't sit on someone else's wheel letting them do all the work, it's not a race, so it's just not cricket.
Have I just been unlucky, or is this normal practice?