The 19-year-old under arrest is Ryan Cleary, who may be a rogue former member of Anonymous accused in May of attacking Anonymous' own sites, including the IRC channel on which it coordinates attacks, according to local media in the U.K.
Various stories raise the possibility that a joint investigation by Scotland Yard and the FBI turned up not the mastermind of LulzSec, but a former member turned thorn-in-the-side of Anonymous, who might have been sold out by members of his own group.
Extant members of LulzSec are doing what they can to add to the confusion.
Anonymous announced in May that "our network has been compromised by a former IRC-operator and fellow helper named 'Ryan,' the group Tweeted.
Unnamed persons, who might or might not be Anonymous, "doxed" Cleary earlier this month, revealing his name, address and other critical information in a document posted on Pastebin, presumably in retaliation for his attacks on Anonymous' IRC channel AnonOps, according to the Tech Herald.
Someone appearing to represent LulzSec posted another document with more background on Cleary, while suggesting other conspiracy theories about why everyone (including them) is behaving as they are. (Everyone either is cooperating with the CIA, is pretending to have been cooperating with it or is "adopting the tactics of the CIA" by accusing everyone of everything at the same time and suggesting that some of the people involved in the conspiracy may not really exist.
"Ryan Cleary is a dissident hacker who attacked AnonOps and was subsequently "doxed". Some accuse Cleary of hacking Sony. However, Cleary is not facing any criminal charges and there is no evidence that he exists. AnonOps hackers may have engineered a false flag attack against their own servers under the name of Ryan Cleary, in hopes that the Sony hack would be credited to him. LulzSec is simply the logical conclusion to this chain of events – a hacker group that breaks all the non-existent unwritten rules of Anonymous in order to regain traction after the failure of #OpSony."
I'm sure everyone is glad that's all cleared up.