batch renaming files with spaces

Why do people keep giving me tons of files with spaces in the filename?

Anyway, here's a good way to get rid of those pesky spaces:

ls * | while read file; do mv "$file" ${file// /_}; done

First I tried using "for file in `ls *`" but of course the whitespaces came back to bite me... This was also true for the mv command. You have to quote "$file" in order for the whitespace ridden filename to be recognised as a unit rather than multiple file descriptors.