I use 'retarded' occasionally online, and it's thoughtlessness, definitely. When I realise what I've said I often go back and edit because I know it's offensive, even to me, but I still think it. On the other hand I'd never even think 'spastic' into a sentence, let alone actually use it. It's odd how they're both used in the same way, they were both used as commonly as 'loser'/'idiot'/'wanker' by people at school, and yet one is still completely taboo for me.

And now I wonder if 'insane' is similar. I often say I'm insanely happy, or god that's insane. It's not in a derogatory way, and it's got little to do with what 'insane' actually means, but still.