I've said this elsewhere, I'm sure.
I've personally lost data on 2 USB sticks now -- they just blanked themselves. No data recovery was possible, scan utilities said there wasn't a single byte of data on 'em. I also know a couple of folks who have experienced similar USB stick failures. There's no predicting these things -- a 512Mb USB stick I bought maybe 8 years ago is still going strong, with no errors; the lost sticks were fairly recent (4Gb) from different manufacturers. They still work OK, but I can't trust 'em not to blank themselves again. I always use the "Safely Remove Hardware" option, I don't just pull 'em out. If your only backup copy is a USB stick then you could find yourself in trouble one day, is all I'm saying.
I have 8 USB sticks now, and cycle them each day. If another goes kaput then I probably haven't lost much. I also have 2 external USB drives which I backup everything to every other day.
Emailing files to myself, super easy, and instant (just did it!).
Dropbox, also super easy, although I notice it can take time to confirm the update, e.g. if I'm backing up a large zip file it can take a minute or 5. I think you have to wait for the confirmation before you shut down for the night, otherwise the transfer can't complete.
-Derek