The cons of speed dating include an unreliable ratio of men to women and the requirement to spend five full minutes with someone with whom one has no chemistry. Pros include the ability to weed people out quickly or at least see if the other person could fit one's list.
When companies and organizations try to set up speed dating events, they have to rely on marketing to bring in a helpful ratio. Smaller events that only feature a couple of men and a lot of women (or vice versa) are ultimately frustrating to both groups. Also, sitting across from someone with foul breath, a need to share every painful moment from his past, a total lack of conversational skills or with antisocial tendencies makes for an excruciating five minutes. A person could also run into an old flame that way, which could become extremely awkward.
Speed dating does offer the benefit of a swift look at several different prospective dates. It doesn't take that long to determine whether the other person is definitely not worth pursuing, but it also doesn't take long to spark some attraction and at least get some idea as to whether the other person has at least some of the criteria one is looking for. The benefit of quantity is definitely one of the most popular pros of this type of dating.