Talk about defeating the point..
"You are using the letter of the law to defeat the spirit of the law"
What they did probably removed a huge amount of computers from that botnet. Yes the BBC had control of these machines, and could have done massive amounts of damage - but considering how easilly the BBC got access to this botnet surely you'd be happy to see it removed from the internet rarther then still out there waiting for letters to filter through ISP's crappy legal dept's and then slowly out to the users in all those different countries?
If they had gone onto peoples computers, hunted for illegal material and then posted that information to law enforcement agencies - yes that would've gone too far - but they didn't. They acted IN the public interest, FOR the public good.
Seriously, get over ourselves, stop lapping up the Wackie Jackie hype and realise that there are exceptions to the rules and discretion should be used in some situations.