The very first exchange I ever did, it was the MOD OF THE EXCHANGE who wrote for me and did that!!! It was a wank-themed exchange, wherein you could specificy whether you wanted solo wank or mutual, and if mutual, which pairing. I requested, very specifically (or so I thought), H/D mutual wank and got DM solo wank while sort of noticing in passing that HP was walking by or something, with an apologetic note about H/D squicking the author. So why, as the mod of the fest, s/he didn't give my request to one of the five hundred million fangirls or -boys who isn't squicked by H/D, I'll never know. But that's neither here nor there. :P

I always think I ask for too much, too, and then I see other people's requests after and realize with horror that I forgot to specify, like, "no Roman showers" or something, and panic. :P But then, there will always be someone who left a longer and pickier request than you did, I'm sure. :P