A study completed by The University of Texas School of Public Health (thanks to the Houston Chronicle for the tip) found that women are safety-cautious when meeting people from online dating sites, but once they interact face to face, they make riskier choices as compared other single females.
The survey asked 740 women their sexual and safety habits when it came to meeting men from online dating sites for a five-month period. Of those women, almost 600 met a gentleman face to face from their online interactions, with 30% having sex n the first date. Of the women that had sex, more than three quarters didn't use a condom. This contrasts greatly with other data from the Center of U.S. Disease Control which found that almost 50% of women under the age of 30 use a condom when first becoming intimate with a new partner, as well as a survey from ABC News in 2004 that showed 17% of all women have sex on the first date.
Related: Keeping Safe Online