Casual dating sites
Localfling and others
They're nearly all scams, especially the ones which are free to join and charge ££ per message. In the small print it may say 'entertainment' which is a giveaway and means you have no legal recourse. If it doesn't say that and you've lost £100s or more, then consider suing them; the law's on your side.
I lost £10 or so via other similar sites but I wasn't born yesterday and soon realised a woman who claimed to lived locally was paid by the website owners.
Pros
None
Cons
Everything
Visit LocalFling Reviews about LocalFling