Though "matchmaking" agencies and personal ads seem to be a thing of the past, online dating services are booming businesses right now. Though I have no personal experience with creating personal ads nor using online dating services, I have several friends who do. The majority have had mostly positive experiences and the problems that exist seem to be accepted as given potential risks.
First, there is no way to be absolutely positive that the people who have posted ads are being completely honest. In fact, I think most users expect others to fib a little to make themselves sound as best as possible. Another problem that many complain about from online dating services is that things seemed much better when communication was only happening online or over the phone. Many people I know have been terribly disappointed to find that the person they were so interested in from a distance was not the same in person. Finally, though services like match.com and Eharmony are thriving, there is still a social stigma that comes from admitting the use of an online dating service. It is almost as if it is the admission of utter desperation.
Ironically, we live in a day and age where online dating provides (for some) a physically and emotionally safe alternative to going out and trying to meet other singles in places like clubs and bars. I can personally attest to knowing several very happily married couples who originally connected because of online dating services. I think the pros and cons are probably subject to the users themselves, their expectations, and their willingness to be open-minded.