Both Yahoo Personals and Match.com have received several complaints of this tactic. Some users spam sites with "fake" profiles that are in reality advertisements to other services, such as prostitution or multi-level marketing. A majority of dating sites keep profiles online for months or even years since the last time the person has logged in, thereby making it seem as though they have more available members than they actually do. Many sites offer the option to sort search results based on activity, however. Most sites still have significantly more male members than female.

Most members are enticed to join dating websites with free or low-priced "trial" memberships advertised on many other websites. These trial memberships lack many of the features of the full membership, including the ability to contact other members or reply to e-mail from other members. On sites which require credit card information to join at all, these trial memberships often automatically become full memberships at the end of the trial period and charge the full monthly fee, without any additional action from the member and regardless of whether the member has actually used the services or not. For paying members, it is often unclear whether a potential contact has a full subscription and whether he or she will be able to reply at all.

Even when members' profiles are "real", there is still an inherent lack of trust with other members. Many members misrepresent themselves by telling flattering 'white lies' about their height, weight and age, or using old or misleading photos. Members can, of course, ask for an up-to-date photograph before meeting others. Online predators find online dating sites especially attractive, because such sites give them an unending supply of new targets of opportunity for Internet fraud.

Some sites cater to people with special interests (e.g. sports fans, nerds), professions, political preferences, ethnic groups, conditions (e.g. HIV+, obese), or religions.

Matrimonials Sites are a variant of online dating sites, and these are geared towards meeting people for the purpose of getting married. Gross misrepresentation is less likely on these sites than on 'casual dating' sites. Casual dating sites are often geared more towards short term (and implicitly sexual) relationships.