who_am_i has it correct. Dealing with flags, whether they are legitimate or spam, is just part of what you have to deal with as a moderator. I can certainly emphasize with you though, we site mods have to deal with a lot of bogus flags as well. One thing I will point out is if you get an account that has flagged a lot of content (like 50+ flags) in a very short amount of time, get in contact with a Community or Global Moderator ASAP as they could be running a bot or algorithm, or doing some other sort of hacker stuff.