Don't just reformat the SD card in your Droid or on your computer!!!
With a simple reformat, ALL of your data (personal photos, whatever) is still on the card and is *extremely easy* to recover with a variety of easily available data recovery tools.
Formatting more than once won't make any difference.
What you need to do is find a utility for whatever operating system you have on your computer, use it to destroy the data on the card (by overwriting the entire thing with random data) and then format it.
I use a command line program called 'shred' on my Linux machines to do this. I don't know what's out there for Windows or Macs.