Dunno...I have a small penis and I've never been dumped, I've always been the one to do the dumping though. My wife is beautiful and has had a LOT bigger than me. I think it's more on how you use it because every one of her ex's were bigger than me and I am the first to ever give her multiples (40 in about an hr.) She went into convulsions which led to her having an astHydromaxa attack. I've never given a woman less than 6 orgasms in one session though, that's for sure. I also happen to read A LOT about everything to do with women, so I think that it helps. Oh, and I have scars on the underside of my penis from surgeries due to a birth-defect (hypospadias) which according to my wife is better than the ribbing on a ribbed condom or a ribbed dildo.
My wife tells me that big ones hurt her too much. When we first got together, it hurt me pretty bad when I first went in her because she was so tight and I am (4" long 3" in girth) so figure that out and I had stolen her from her b/f at that time who was 7" long according to her. My wife also gets off within the first 15-20 seconds of intercourse with me where as even masturbating with dildo or
vibrator takes her at least an hr. or so.
But to answer your question, no, I have not heard of a woman dumping a man for having too big of a penis (which doesn't necessarily mean that she enjoys it either) MOST women tend to look at the emotional aspect of the relationship more-so than they do your damn penis size.
Considering that the G-Spot is only about 2-2 1/2 inches inside of a woman's vagina, you don't need to be 10". Also, look at the size of MOST women's dildos, they are usually 6" in length or under (ie...the rabbit). And yes, from personal experience, women DO enjoy having your thrust all the way into them while hitting their clit (which is why I had to shave) because my pubic hair was rubbing my wife's clit raw. After I did that though, she's never been sore.