All - many thanks for the responses
I think I have probably been too concerned about this and I'll just keep doing what I was doing (i.e. giving karma for what
I considered deserving of it and not worrying too much). It's the thought that counts (paraphrasing RWood's words).
I read Cory Doctorow's 'Down and Out in the Magic Kingdom'recently and it may have coloured my thinking about this kind of thing!