Like all things...it's all in how you approach it, interpret it and use it.
If you just go at CL like you're gonna try all the girls on there (or even 1/2 of them), you're gonna come away burned a high percentage of the time. But if you don't just jump in and you spend some time observing, you can quite easily pick apart the "waste of time" ads from the others. I personally always review the ads regularly and get familiar with the usual scam artists, B&S posters, lacklustre performers, etc. Then every now and again you'll see one show up that looks worthy, I'll watch it for a week and see how it shows up day to day and get a feel...then decide if I'll try it out. Not saying you won't hit a burn from time to time this way, but I've sure flipped the balance of good vs burns doing it this way...and I have met a few stellar girls that only ever advertised on CL, that I still regularly see that don't advertise anymore. I like finding the "non-pro" gem that really likes to go and that's my appeal for CL.
Similar to the casino metaphor mentioned previously, with CL...there are risks of being burned bad...or hitting a real jackpot (either extreme end of the scale)...but as I mentioned, I have definitely found "jackpot" gems on CL that make it all worth while for me...
Again...it's like anything, you gotta be mindful of how you use it...