I'm still trying to understand two points:
1) WHO is SPEWS (who is beyond that, who runs that stuff)???
2) WHO uses it??? (I mean: who really big - like Yahoo!, Hotmail etc is
using their list)

I know that several netblocks listed there are really spamheavens (like
Telefonica Brazil), but they are now listing /24 even if only IP in that
netblock is spamming...

They may even be serious, but listing /24 and bigger ranges without
showing the evidence for that listing is really crazy and insane...