In my opinion, tags should represent [i]topics[/i]. That means Data Structures, Dynamic Programming, Geometry, Graph Theory, and Math are fine as they are. Recursion is not really a topic as much as it is a technique, and a very general one at that. We're better off replacing it with more specific tags like "Brute Force" or "DFS."

We should broaden the "String Manipulation" category by just calling it "Strings."

Simple Loops/Simple Math should be combined into one category, perhaps called "Implementation" or "Straightforward."

Simulation is a weird one. I don't think there are too many simulation problems out there, but we could keep it.

In addition, I propose the following tags:
[list][*]Searching
[*]Greedy
[*]Number Theory
[*]Combinatorics
[*]Game Theory
[/list]

Are combinatorics and number theory really distinct enough to be separate tags?

As for a Greedy tag, well, I'm not sure if we really should be having technique tags. They might spoil solutions.

True, they are a big specific. Before we add a tag, we should probably do a quick survey of the amount of problems anyway. If DP is a tag, then I'd argue that greedy is no less of a spoiler.

[i]Any[/i] tag is a spoiler to some degree. That's why I already made them hidden on statements. The real issue is, we'll have to decide what to do if we ever consider displaying them directly in the problems list.

For reference, the current tags:
[list][*]Data Structures
[*]Dynamic Programming
[*]Geometry
[*]Graph Theory
[*]Math
[*]Recursion
[*]Simple Loops
[*]Simple Math
[*]Simulation
[*]String Manipulation
[/list]