I ran into this recently with a very highly rated SP here on Lyla. Since no one else has mentioned this fact about her, I'm not going to either, but this lady was certainly NOT the gal in her photos. I was initially disappointed, but had committed to the date and carried through. Luckily, I was NOT disappointed, and it was a great experience.. I believe.. for both of us.
I can imagine how some would be put off though... I've had bad experiences in other locations.
This has been discussed in another thread, but I can totally see where the advertisers want to both protect their privacy and attract the right dates.. maybe a little photoshop or a 'representative photo' isn't a bad thing.. but it's also not the best thing.