Hi, I'm new to this hobby and am concerned about contracting STDs from a provider.  Have any of you contracted a STD from a provider (when using protection).  Is this a real risk?

And believe me, most providers are just as concerned about getting STIs from clients. Hookers are not STI-ridden women simply because they're hookers.  Your risk of getting an STI from a hooker while using proper protection aren't much different than your chances of getting an STI from a civilian, assuming you're using protection with said civilian.  

define low.  is it one in 20, one in 100, one in a thousand, one in a million, etc?

Different activities carry varying risks for different STDs.  Start with a general Web search for "STD risk".

I hear vague statements about risk that no one can quantify.  That should be a red flag to all johns.

...all over these boards about std's. Do some research. There are links to the CDC and many other info sources in the discussions here that do give stats and plenty of help in making decisions in regard to this hobby and how to reduce risk.

Do some research. the statistics are out there. Proper condom usage doesn't care if you're a hooker, john, or a regular civilian.  if you use them properly every time, risk is mitigated at the same percentage.  This is assuming that the condoms are being used properly, and we aren't talking about STIs that condoms don't necessarily prevent, like HPV or HSV.

Dude, there is a plethora of information about STI exposure risk, contraction rates, etc.  Databases full, even.  

in other words they do not prevent the diseases you really do not want

What you just said makes no sense whatsoever.  Condoms prevent HIV for Christ's sake. Most of the population of sexually active adults (around 80%) have HPV, and the number is similar for HSV.  Certain types of HPV cause cancer in women only.  Most cases of HPV, once treated, go dormant.  Most people who have HSV got it as a child. Cold sores are HSV.  

Erin if you haven't noticed yet this is the boards new resident troll . He's already had about a half dozen posts deleted from this board alone .He's not worth wasting your time or energy trying to debate or reason with . Save that for people that have real questions and are here to actually learn .

i know, I know.  Sometimes i need a reminder.  Thanks, kazz.

lol , happens to the best of us Erin