Anonymity + Greed = Spam (Thanks to @mblumenthal)
Anonymity + Pride = Trolling and off-topic rants comments
Anonymity + Gluttony = BitTorrent running 24/7
Anonymity + Sloth = Spending all day watching Youtube videos
Anonymity + Lust = Watching lots of porn
Anonymity + Envy = Comparison shopping and stalking exes and potential dates on social networking sites.
Anonymity + Wrath = Racist, homophobic and nationalistic comments and defacing websites because one can.
And, for Randy at ThisIsTrue.com, maker of Get Out of Hell Free cards:
Anonymity + Stupidity = Misinformation, badly written Yahoo! Answers questions and answers, and forums full of people half-solving problems and no real fixes with understanding of why the problem happened in the first place.