The really depressing thing is that this applies to all walks of life - landlords and tenants, estate agents, even recruiters. From my own experience of runnin

The really depressing thing is that this applies to all walks of life - landlords and tenants, estate agents, even recruiters. From my own experience of running a micro-agency, the "1 in 20 sociopaths" rule absolutely applies. I had three or four joyous years where I had nothing but satisfied customers who were happy to pay (not, it must be said, in a particularly timely fashion for the most part, but they paid without griping, which is the main thing); sometimes they were demanding and wanted an awful lot for very little money, but even in the worst cases, we got there in the end, and the relationships were good enough that they persisted regardless (and a lot of the time, the really great clients - who were not demanding and paid well - balanced out the other ones, so it all seemed good enough on the whole). Then I had two awful clients in the space of three months - we did exactly what we always did, but they were, to be frank, just terrible people who didn't want to be helped, demanded the impossible, and then refused to pay when - unsurprisingly - we failed to deliver; with one, we ended up splitting the bill, and the other remains a bitter ongoing dispute. (There were actually useful lessons to be learnt in both cases, so every cloud...) Speaking to other people in a similar situation to me, the consensus is that I was just incredibly lucky for those halcyon years where it all just worked: one guy in particular said that his general expectation, based on his experience, is that at least one client will try to screw him every year; another guy I know builds a remote kill-switch into everything he delivers for precisely that reason (which I have always thought is horribly unprofessional and unethical, but I can now at least see where he's coming from). Many people are good; a surprisingly large proportion of people will, even if they are good, try to get away with as much as they can regardless; and some people are just very, very bad.