Reports made to Google Groups are a complete waste of time.
Google will only cancel *that* account (without blocking the IP
It takes the spammer 30 seconds to enable *another* account.
That is, ZERO real effect.
It should also be noted that each time this is done
plonk files could grow by one item.
For Blogspot/Googlepages spam, report those to
mailto: XXXX@XXXXX.COM adsense-abuse@ google.com
That puts his site into Google Hell (screws up his GoogleRank).
The most effective effort you can make
is to do a reverse-DNS on the NNTP-Posting-Host
and report abusers to their providers.
This assumes their ISPs aren't complete rogues.