I don't know. I mean there's definitely internet embellishment, but even so, it depends a lot on the kinds of cyclists you're encountering. On the trail here, I pass lots of riders when I'm "strolling" at 15-16, but I guarantee you none of them are the kind of riders who are serious enough to post on a cycling message board. I'd guess that the same applies in your area.

On the other hand, at the twice-weekly shop rides I frequent, I ride with the second-slowest group, and when I can stay with them, my average on those rides is in the 18-19 mph range (non-embellished numbers, I promise you). The 3 faster groups average 21 to 25+ (most of them are racers). Granted, those are group rides and they include drafting. Solo rides are something else, and I can manage in the 17s for up to 50 miles (with a couple of rest stops), but I don't think I'm particularly fast by any means. On those occasions when I'm alone on the road and encounter one of the faster riders from the club who is also riding solo, they're always riding at speeds I can't even hope to keep up with.

So maybe it's exaggeration. Maybe it's conditions. Maybe it's the people in your area.