USB Drives always need to be formatted to delete items I have a MacBook Air running Lion. Issue is I cannot delete things from USB sticks. The icons disappear but if I try to copy something on I get a not enough space error message.

I can format the stick to delete everything, but it seems I must do this every time.

Can anyone help me out?
The next time you have your USB stick plugged in, open up Trash in the Finder, and you'll see the items that you have deleted in the trash. So, although you are "deleting" files from your USB stick, they are still there, and taking up space. You need to delete the trash when the USB stick is plugged in. This will solve your problem, as long as you remember to regularly empty the trash.