2. Sometimes they pretend to be an "official" and "exclusive" recruiter for the company "X" but after a brief search you can find out plenty of ad for the same position around Internet;
3. Related to the point 1 and 2, sometimes, when you require information about the position or the company, no information is provided because the position doesn't exist, the think you can contact directly the company that's looking for employees or both these reasons;
4. Sometimes recruiters don't know what are speaking about/ what they are looking . I can testify hundreds of example related to IT.
5. Sometimes they aggressively try to contact you by phone even when you, after receiving necessary clarifications,you tell them you are not interested to the position;
6. Sometimes they are spammers, mostly spammers by mail and spammers by Linkedin. About Linkedin, using it as a type of FB surrogate, sending tons of links with private preferences, kitties, funny viedo on Youtube, photos of celebrations in their offices, advertisement ot their customers, etc. Why they don't send the only thing you want from them ? I'm speaking about job specs of course.
It is extremely rare to come across a tech recruiter who has actually worked in IT and has a minimal level of understanding.