Blockchain.info, aside from being a great tool and web wallet, offers and advertises a coin mixer service - or to put it in plain English, a money laundering service. Under what jurisdiction is money laundering legal??
It's about privacy. Addresses can be tied to users (like how you put a vanity address in your sig).Now if you go and purchase some boner pills, the whole world will know about it.
It's not just addresses - groups of addresses can be be identified to the same user. Go here and click on the owner icon: http://blockviewer.com/#/owns/1ELECeJompinDox61L73eAUyaWpe3Q5HZB - you can see 190+ addresses has been linked to him as well! In fact, the tool even identified his screen name (look at the line label pointing from his address to the owner icon) so he's explicitly identified.
EDIT:
What's even more damming is that another address was explicity identified to be from the user "flatfly". So the OP also owns flatfly username too -> https://bitcointalk.org/index.php?action=profile;u=52782
Which is totally public information... But congrats on your couch detective skills
And nice tool by the way.