No need for the judgment guys, let's keep it polite. As for whether it's dangerous or not, well it depends how hard the person is pushing on it and (the members) are right, if it hurts, then the lady doing it is not doing it correctly and you should tell her to stop right away. The other possibility is you could have hemmoroids or an infection (both make this experience very unpleasant, so treat that first if it is the case). And for god's sake if you want to be sure to avoid infections, bring you own vinyl gloves, never let them use a bare finger! If she has long nails, forget it, way too risky!
If the lady uses a soft touch it's good, but very few women (MP's) have experience or know a lot about that particular part of the anatomy and then again, neither do we (men). After all, it's the male g-spot.
Also, it's goal is not to increase circulation, but to stimulate and generate more semen. The more semen, the larger the orgasm. Aha!
I found some helpful links (the internet is wonderful for that you know).
http://en.wikipedia.org/wiki/Prostate_massage#Risks
http://www.whitelotuseast.com/SacredSpotMassage.htm
http://en.wikipedia.org/wiki/Semen#Composition_of_human_semen
http://en.wikipedia.org/wiki/Seminal_vesicle
It's a complicate piece of machinery down there guys, thank Christ we have a manual!
As for providers. Some of the best have retired, but it pays to do a search. Currently I only could recommend (as mentioned in my Best massage 2008 posting)
Best PJ (prostate massage): Alyssa a.k.a. Alicia, Elite Massage
She does a good job.
Also, Lissa, independent of Craigslist
Had an appointment recently with her and she mentioned afterwards that she does the prostate massage, but not sure if she has gloves so better settle that when you contact her.
Good Luck.