Bad Sectors

I have a hard drive that dos said had bad sectors. I booted the machine with a
slackware live cd, and ran badblocks on it. badblocks -svvw

Afterwards, it found no bad blocks, so I formatted it with ext3 and I'm using
it now. It seems okay and I have filled it, deleted stuff, then filled it
again. What is the deal with bad blocks? Are they really repairable? Are they
not being used? Or am I going to be having problems soon?

I don't know how the actual hardware works...

nathan