Obviously everyone has to judge these things for themselves, but I think some people are more reasonable than others. Take a look at these stats re: HIV, the STD feared the most:
http://www.cdc.gov/hiv/policies/law/risk.html
Keep in mind that's the number of occurrences per 10,000 events with someone who has the HIV virus, *not* 10,000 events randomly selected from the general population or the population of prostitutes. For oral sex the incidence is so low they can't put a number on it, even though they rate other sex acts as a single digit. So 1 in 10,000 with an infected partner would probably be on the high (pessimistic) side.
But what is the probability of encountering an HIV infected provider? The CDC says this about HIV rates among women in the US:
"At some point in their lifetimes, an estimated 1 in 32 black/African American women will be diagnosed with HIV infection, compared with 1 in 106 Hispanic/Latino women and 1 in 526 white women."
HIV infection among prostitutes is thought to be about the same or even less (because they are more cautious) than the general population. Assuming this is true then getting HIV from uncovered oral sex with random (white) prostitutes would be once in 5,260,000 times.
Now some might say one in five million is still too much risk. But people take one in a million risks *all day long.* The chances of being struck by lightening, or in a traffic accident, or falling down stairs, etc.
So this gives some perspective as to whether BBBJ presents a reasonably low level of risk.