) We do not believe there is a pressing need for more specific tags, we like to keep tagging as simple as it can be. The simpler it is - the better, since it lowers the learning curve, and makes tags a lot less cluttered.
I understand what you mean, though, but I personally believe that no tech, no organisation method can be perfect. People can simply use their eyes to judge the content they see in the results, or exclude group sex tags from their searches. Either way, we do want to strike a balance between the level of tag detail, and simplicity. Cluttered tags aren't any good either, and are a nightmare for both uploaders the moderators to maintain and enforce with little to no actual benefit.
There may be tags that correspond to group pictures, orgies, duos, triples, and so on, which may assist people in further narrowing down the content they wish to see.