I worry about my hard drive crashing and losing all of my images. (For the sake of discussion, lets forget about backing up images on a DVD.)
I could be wrong (and set me straight if I am) but I tend to think that Picasa and Flickr are the best places to save, back up and store your images. It'll probrably be hard to find someone who has a lot of experience with both image hosts, but if you are that rare person who has used both extensively, which one of the two do you prefer? And why?