I think it's a myth, personally.
While hanging out at Denny's after a 'Rocky Horror Picture Show' performance, one of the girls opened up a condom and put it on over her foot and leg, all the way up to her thigh. Not a single tear, even with the ballet flats and fishnets she was wearing.
A friend and I also once decided to use them as water balloons, and began to fill our first one up in the bath tub. The sonofabitch filled the entire tub before it burst.
And our smooth as velvet insides manage to break them while being worn by something that will never be larger than a breadstick? Doesn't scan. Use another form of birth control and be more discriminate about partners.