A 'rich' person is just somebody who has at least twice as much money as me. If I earned $100 a month I would think everbody in the UK and US was rich. A worse problem in the UK is rather that we continue to tax the poorest among us.
The tax increase to 50% will raise very little money, when one allows for the changes in behaviour that it will cause, loss of sales taxes on spending etc.. Its only purpose is to divert attention from Governments' chronic and puerile refusal to do grown-up budgeting of the form (1) how much money can we reasonably raise? (2) how can we best spend it? The fact that a Government's borrowing power is almost (but not quite) limitless deceives them into thinking that borrowing doesn't count. They use stereotypical Teenager Economics.
I don't think the 50p tax rate on high earners is a serious attempt to raise revenue. I think it's an early sign that Labour might revert to class warfare politics in the run-up to the next general election.
The way I see it, Labour only know two ways of winning a general election. The first approach is the recent 'New Labour' way, positioning itself in the so-called centre ground with a Tony Blair type leader. The second approach is the more traditional class warfare approach that was reasonably successful for Harold Wilson and Jim Callaghan in the 1960s and 1970s.
For Labour the first approach is compromised by the fact that the Conservatives have decided to adopt it as well, and have got a Blair-like figure in David Cameron. The second approach is more viable than it may first appear. Gordon Brown is closer to the Wilson/Callaghan style than he is to Tony Blair. Labour got into trouble with the class warfare approach in the 1980s due to the infiltration of the 'Loony Left' making them appear unelectable, but the Loony Left problem has now faded away to a substantial extent. The Conservatives are also currently being run by a bunch of posh people for the first time in about 45 years, which may make the Conservatives more vulnerable to class warfare politics.