The downside of 'friends with benefits' - CNN.com
This lack of vigilance about STDs is especially true when the sexual partner is a former boyfriend or girlfriend, she adds.
"We're finding that 'sex with the ex' is a very common experience," said Giordano, who's been studying the group of Ohio youth since 2001.
"It's seemingly safe, since they used to be your girlfriend or boyfriend. But of course you don't know what they've done since you broke up. You don't know their full portfolio of partners," she said.
