I suspect so many people wouldn't be outraged if it were the BBC than Sky, but whatever. I want to make a few additional points.
UPDATE: Another point added at the end.
First: the BBC pay me too, usually to come on a news show and offer an opinion. This is arbitrary too; sometimes they pay and sometimes they don't. In fact most people who go on television or radio don't get paid as they're not professional commentators.
Most people in the media who guest on other media DO get paid however, and they assume that everyone knows they're getting paid so no one says anything. But I think that's hypocritical - why don't people declare every instance they're getting paid for their opinion? If you assume that getting paid for it will make you biased - why wouldn't that apply to going on BBC 5Live or Newsnight?
Secondly: I'm not being 'sponsored' in the conventional sense. I don't get told what to say. Sky merely want to me to report from a programme on what people on it are saying. I frequently throw in opinion or links to Liberal Conspiracy that refutes what someone might say. They don't have an issue with that. So are Sky sponsoring me linking to Liberal Conspiracy? Of course not. It is not sponsorship in that sense.
Third: I don't know about others but I usually start off by declaring something like: "I'm going to be live-tweeting the Murnaghan show for the next two hours on behalf of Sky". In fact, journalist Rowenna Davis said that too, when she was queried by Paul Lewis. Isn't that a declaration of interest?
Fourth: People seem to think I'm somehow "promoting" the show - which is absurd. People who state they're reviewing papers on Sky do more promotion than me! My main job, as I see it, is to report on what people on the programme are saying, and offer my opinion on it. It's neither positive nor negative towards Sky.
I think it's absurd to think I've broken some ethical code just because it's Twitter. Sure it's more personal and direct, but I usually judge someone's tweeting by its content and usefulness, not who they are paid by.