Last night Anonymous issued a statement branding the UK arrests "a serious declaration of war" against the group of internet "hacktivists".First of all I'd be interested to see how Anonymous can issue statements, because it isn't an official organisation with a spokesperson to present the groups decisions to the world- it's a bunch of youngish men who meet online anonymously to discuss shit and share porn.
In fact when looking at the home of Anonymous- 4Chan's /b/ board- you can see that the main interests of Anonymous are getting a laugh* and wanking. To the extent that they're into hacking it largely seems to involve invading the Facebook accounts of teenage girls they know, not bringing down the world financial system. It isn't that they can't cause problems for people- it's just that the people they cause problems for are more likely to be 11 year old girls they are cyber stalking than the Director of Public Prosecutions.
Some people from Anonymous will try to hack UK websites in retaliation for the arrests- but so what, it isn't as if their previous attacks have caused huge disruption- they brought paypal down for a few hours- oh no. I suspect most of the members are actually jealous of the arrested hackers seeing as when they go to prison they are likely to be the only members of Anonymous to be having regular sex.
* Some of the stuff is quite funny- the 'Pedobear' meme for example originated there, although that is at least partially a response to the amount of child porn that gets posted on there.