I wanted a camcorder I could carry with me. I'm fed up with missing filming opportunities because I didn't have a camcorder. Last year I bought an XH A1 and... it's too big to take along on a day out. So I got a Canon HF11. Both are wonderful cameras and far from the most stupid thing I bought in the last year.
Now the Canon spare batteries for the HF11 are outrageous and so I bought a no-name which cost £40 instead of £100 only to find that (a) you have to have a separate charger because the Canon won't charge it (b) there's no battery info in the viewfinder and (c) it rattles a bit when it's on the camera.
My most recent stupid purchase and a waste of £40 which I could have put towards a Canon battery.