Hi
 In 18months (and lots of tours) I have only come across two nutters. One was my own fault as my head was telling me not to accept the booking but for some reason I did anyway. Lesson learnt. Listen to your inner voice. If something feels wrong then do not go ahead.

As for getting bookings being a size 18 - 20. I am an 18 and get more than enough sweetie

I have never heard of anyone catching an STI from having their boobs sucked and am pretty sure that unless you have open cuts then their is no problem at all. Receiving oral should again be fine as long as he doesnt have coldsores or open cuts and neither do you.
Why not pop along to your local GUM clinic where they will happily give you all the facts on Sti's so you are better informed.

I've never run into anyone really dangerous, I had a horrible experience with a man who was verbally abusive and intimidating but it didn't go beyond that. I have had clients try to bully me into providing services I don't offer, if you tell them off usually they back down, and I have had to throw men out a couple of times for being rude and disrespectful.

When I asked at the clinic they told me that receiving oral without protection does carry some risk. Herpes, Syphillis and Gonhorrea can all be spread that way, although the risk is lower than other types of sex and obviously herpes and syphillis you would usally be able to see the sores and refuse the service. If you're not comfortable offering it though, don't. It's not a deal breaker for a lot of clients and there are plenty of ladies that don't allow it.

Personally I'm happy to receive oral as long as I can't see any sores on the client's mouth, tongue or lips, and as long as they have good oral hygeine (as stds aren't the only thing you want to avoid, any kind of nasty bacteria down there is no fun).