I'm not crazy, but you wouldn't know it if you logged into my Garmin account. I use my Edge 500 when I'm on the trainer as a timer and for the cadence function. When I upload my data, I get the map of my route... and clearly I am a crazy person riding around my yard:
I guess the GPS isn't as accurate when you're not actually moving, and probably somewhat obscured by being in the basement. I have A LOT of files that look like that, so if the people at Garmin are mining my data, they are going to wonder about the insane person that keeps logging miles riding in weird patterns in a tiny area.