(I'm coming at this from a US perspective..but something tells me 95% is applicable in IRL in this context).
There are several "have an affair" style websites over here- they encourage the guys to buy "credit" for unimited communications yada yada- all rackets ( note I didn't use the word "scam"- you may have a 2% success rate).
Most of the casual encounters postings on Craigslist are cam girls- they'll lead up on & want to "get to know you" before meeting- normally at a rate of $10/min- for most part( ~99.8%) pure fraud. ( The Escort listing section of CL closed down last year, they capitulated to the moral majority- very dangerous precedent in the land of free speech!).
Some listings that offer escorts are thinly veiled fronts for phising scams- you need to "get verifed at this website first"- guess what info they're looking for!
Bottom line- the web is a very shallow sea teeming with sharp jawed predators- if it looks ( even remotley) too good to be true, vast majority of time it will be- stay safe & use yer noggin!!