There is no one group called "Anonymous". That's the point of the name: ANYONE can use it. There's probably at least 50 groups who call themselves Anonymous or go by that name, because, once again, ANYONE can be anonymous.
There are a few "big" groups who call themselves Anonymous. They tend to either be anarchists (the political kind) with a message (even if it's not a particularly helpful or coherent message), or they tend to be jerks who try to ruin other people's lives.
They are good Anonymous groups and there are bad Anonymous groups. The Media, with it's 40 something year old anchors who think "Angry Birds" is "Hardcore" and have trouble with their email accounts still can't quite get their heads around the fact that, yes, Anonymous can mean anyone or anything. There is no centralized HQ of Anonymous, there never was. They don't have official spokespersons, they have no set member list. They just call themselves Anonymous because it confuses the authorities and gives them safety through numbers.
Basically: They're internet users who try to use internet and group tactics, combined with anonymity to achieve a particular goal. Sometimes the goal is political - like backing Julian Assange or trying to get Brian Manning freed, or trying to take down Internet Security firms that try to track it. Sometimes the goal is just horrible meanness on a mass scale - like issuing death threats and publishing the address of a THIRTEEN YEAR OLD GIRL just because they didn't like the song she made (way to go, what brave, brave men they are, picking on kids!).
You can't say they are evil or good anymore than you could say "Americans are evil or good". They're a diverse bunch. Some are activists with a message. Others are just.... jerks.
EDIT: As for the future of Anonymous - for the meanwhile it will continue. But they had best be warned - the public (and they are not the public) can only tolerate so many of their antics. When they use their collective methods to go after the powerful or the evil, they get points. But, and this is the part they don't understand, they also lose points whenever they do a jerk move (like the aforementioned picking on little kids in the name of laughs, which is a jerk thing to do if you have even an ounce of morality). Remember, the State still exists. Anonymous might think "we ain't afraid of THE MAN", but when the Man decides to play tough, the Man can be pretty damn brutal. Right now, the Authorities allow relative freedom on the internet because the pros outweigh the cons. If all these Anonymous groups start causing too much Havoc, then the Man will come down on them. Want to know why Anonymous groups aren't very big in China? Because the Government of China controls the internet with an iron fist and activists are routinely arrested. Do you want that to happen in the US? Or Australia? Or the UK? If you insist on disrupting society, remember, society can bite the hell back, and you might just scare enough people into deciding that Government intervention and control of the internet is a "good" thing. Of course, it wouldn't be, but you do realize you can't push things too far. If things get too out-of-hand, the State has ways of controlling the population, and something tells me that you folks aren't the type with the physique to fight back (neither am I for that matter).
Just a word of warning to Anonymous (and I am aware that anyone can be Anonymous) - you are only anonymous because of the way the internet is set up right now. That could change faster than you know. You have less power than you realize - remember, the internet depends on Hardware - and cables can be unplugged. Your actions won't destroy the internet, but your actions could give the government the excuse to create a federally controlled, restrictive internet. The authorities have let us have this free internet because the majority of us behave. If you don't, you just might give them the excuse to take it away, and believe me, THEY CAN. All it takes is a couple of bills, and couple of laws, and men with guns seize those servers. And the public might just be cheering for them to do so. You can't act with impunity. No one can.
