Most, many, some, few, none??

I have known quite a few who were getting off big time during anal with the aid of a vibrator skilfully applied. There seem to be less who just get off without additional stimulation, although I have known some ladies who liked the feeling of just being taken, even if that didn't get them to come.

....for females, the proportion who have had anal sex with a male increases from 2.4 percent at age 15 to 32 percent at age 22–24." One in three women admits to having had anal sex by age 24. By ages 25 to 44, the percentages rise to 40 for men and 35 for women. ..

Alone, its kind of hit or miss. With a little extra stimulation (playing with my clit, DP, stuff like that), I'll cum really hard. I can only do it one or two times before it gets to be to much though, sensation-wise.

......just anal with no other stimulation going on not me personally.  
I have 2 friends though who do cum JUST from anal to which i'm a bit envious of lol.  
"Getting off" with anal + clitoral stimulation is extra good though .

and sadly for the DC guys, she lives out west and doesn't travel. And, she admits that once she starts, she just keeps going.

Undoubtedly "some".  I rarely ask for it but I have had a few ladies who agressively push for it when I am with them, even though they know I am indifferent. I have to assume that is a sign they like/prefer it. I'd guess somewhere 10 to 20 per ent maybe.