I’m sure the answer is yes, of course, but now the website Prolific Academic reports how many people on THEIR site participate in other sites. The link to the current status is here.
When I last checked, less than 1/5 of the Prolific Academic universe also work at MTurk, which isn’t surprising since many PA workers are British. Next is ‘swagbucks’ (well, next is ‘other’, actually) and I’ve never heard of that one. Crowdflower and Survey monkey come next.