Reporting things and breaking stories isn't really their specialty, so far as I can see.
Still, it doesn't seem like they make up much (apart from when they want to make jokes).
“TMZ is mostly just kids yelling questions at celebrities in airports, isn’t it?”
Technically, yes. Ambush journalism. But I wouldn’t treat TMZ as small time operation. Here in L.A., I personally know some of the valets who have their number on speed dial, and they get paid cash if they park the cars of certain celebs. Same goes at Tom Bradley Terminal at LAX with their customer service clowns.