Although I don’t think its quite there yet there is always a possibility, remembering that taxi drivers where once doing very well, and some still do make good money in London and Glasgow, but not the way it was. One of my custies used to be taxi driver and he said there is just no money in it now, as there are too many people at it.
I could see this happening to any service trade, like a mini recession for an industry. (Corny I know) but when the times get tougher, the tough get going. Its in these times that the weak and ones that cat be that bothered when things are good that fail and end up packing it in, then the cycle started again.
The problem that taxi drivers have is the there job involves most sitting around, and suits allot of well lazy people, but people who don’t really have a good work ethic might find taxi driving ok, but with window cleaning, they would quit in a week as it does have it challenges, and evolves hard work.