People appear to have been sending very large numbers of addresses dust as a way to break anonymity. Granted, they also may have been doing it as a way to get signatures from scriptPubKeys due to the 'R' re-use issue, but the script would use bitcoind to spend the dust which is known to not be vulnerable.

Also there's lots of pretty much unspendable dust out there from Satoshidice and others, and again such a script can help.