Updated opinion on review websites:

Epinions - very hard work but once you’re established it becomes a regular source of income (not a large source of income, but regular) even if you don’t keep writing new reviews. If you do, of course, your income each month should increase. If I hadn’t managed to get a couple of “Top Reviewer” hats though my income would be far less and I probably wouldn’t have stuck with the site.

Ciao - can earn you a bit but really not much point for anyone outside the country the Ciao portal is set up (UK, France, Ital, Germany, Spain, not sure if there are any others at the moment). You have to have a bank account in that country to get any money. Unless you churn out reviews there’s no residual income.

Dooyoo - good for UK writers and okay for others due to the Amazon vouchers, a tiny residual income if you don’t keep reviewing (but Dooyoo “Miles” expire after a certain time, so without continual additions to your review catalogue it’s extremely unlikely that you’ll ever reach payout level.)

Shvoong - not really much good for reviewers, if you write scientific abstracts that become popular you might earn a bit.

Personally I’ve given up completely on Shvoong now and basically stopped writing for Ciao and Dooyoo. This is because Epinions’ rules on cross-posting have changed (original content being so vital nowadays for search engine rankings) and for the amound of money I would get from Ciao and Dooyoo, I just can’t be bothered to rewrite each review so I can post them there as well. Epinions is where I earn most and am most established, so I’m sticking with them. I may pop in to Ciao and Dooyoo from time to time, perhaps adding the odd review here and there, but not regularly.