As already suggested, I considered the original 2011 Cyber Attacks Timeline graph by Thomson Reuters not enough complete since it did not show some important attacks occurred during this tremendous 2011. This is the reason why I decided to draw an enhanced version which shows, according to my personal opinion (and metric), the list of 2011 major cyber attacks both for size and impact. Moreover in this version I added the cost of the breaches (where possible), and the alleged kind of attack perpetrated.
Update June 29: 2011 Cyber Attacks (and Cyber Costs) Timeline (Updated)
I found this interesting graph from an original Thomson Reuters post, showing the timeline of the major 2011 CyberAttacks.
The graph shows all the main Cyber Events of this tremendous 2011 up to June, the 16th. Actually to be perfect it should include also the infamous Epsilon Data Breach, happened on March, the 30th. Probably it had a major impact on the U.S. rather than in Europe, but it is clear that the aftermaths of this breach will last for years in terms of spear-phishing attacks tarteting the affected users.