Hi Nirowan -
Generally, buy-outs are for commercials, whereas film work has a flat rate. However, sometimes actors sign a contract for film work where they receive a percentage of box-office takings; although actos in that position would usually be a fairly big name. For example, Alec Guiness got 2% of Star Wars (makes you want to weep, doesn't it, you could probably buy your own country with that kind of money).
Re: the ethics of demanding repeat fees as oppose to accepting a buy-out. Equity are always banging on about this, and of course in theory they are right. Yet I've always found it rather ironic, because you can only really 'demand' anything when you're an established name, or at least well-known within the industry. If you haven't done any acting work for a year or so, and you're earning £6 per hour in a call-entre, and then someone offers you £2000 for a day's work, are you really going to say "Thanks, but no thanks - I demand repeat fees." Of course not - they'll just hire someone else. That is reality, however unpalitable it may be. Years ago it was different, as repeat-fees were the status-quo. Obviously it's sad that things have changed, but that's the nature of life. And as for the idea that all actors (note; 87% of Equity members earn less than £10,00 per year from acting) should group together in some kind of noble, agit-prop army and say 'we refuse to accept buy-outs', all I can say is, get real.
It would be nice, but it's simply never going to happen - unless you're James Nesbitt or Jonathan Ross. Who said life was fair!!