I'm enjoying some incredible losing sequences at blitz. Was 1189 a few days ago, now down to 975. The funny thing is I've yoyo'd between the just under 1200 down to under 1000 a couple of times now. It's like when you go below 1100 the opponents become harder...
It's because that's the area where most cheaters are. Especially when you play Tournaments. If I face an opponent below 100 ELO under me, I automatically know I'm going to have a hard time.
I regularly lose to players under 1000 rapid when playing unrated. I'm obviuosly no great shakes, but find the unpredictability of lower ranked players, difficult to play against. Once players reach 1200 or so, they tend to stick to book moves and predictable lines more. I imagine this changes again for players, say 1600 or so and above; as their game has developed beyond the "learnt" lines.