It's not the same as a personal loan. Here's the official description by HMRC:
http://www.hmrc.gov.uk/ct/managing/director-loan.htm
So basically, Jimmy Carr's bank account is actually his company's bank account, but he will be using it as his own. This means it is a director's loan, and thus the money he has been spending is not liable for income tax.
His company is offshore, so is not liable for UK corporation tax. He (or probably more likely, his accountant) has chosen to register his company in a country that taxes corporations and director's loans very lightly.
I know what a director's loan is, I'm a company director. You have to pay it back to the company on time, or pay tax on it if you don't.
Anyway the point is, this article is not about Jimmy Carr or the K2 tax scheme and there is nothing suggesting that the 148 staff at BBC are using this. It reads to me as if they have just set up a UK company, pay 20% corp tax (or 24% above £300k) and then the company will pay them their tax free salary allowance of £7,475 (depending on year end) and the rest is a dividend which they will pay 25% tax on, for example, if it's the higher tax rate.
It depends what the salaries in question are but I don't think it's as bad as the Daily Mail are making it out to be.