[rpwilcox]

Right, but if there's high turnover there's got to be an underlaying cause. (Which maybe the business itself doesn't know).

Maybe they don't pay enough, or have too many deathmarch projects, or office politics gets in the way too often, or maybe a few rounds of layoffs

Regardless, if a lot of people have left before you, there might be a reason for that, or at least it will have a factor in your environment there. (Example: A recent round of layoffs might mean a 3 person department is asked to do the work once handled by a department of 10)

[BadassFractal]

All fair points!

What is the incentive of the recruiter to tell you the truth? What if he says: "Everthing's great!!!", you can't really hold him accountable after you signed up for the job. They're salesmen. Is the idea to look for subtle indications of not everything being great?

[cpeterso]

Recruiters are salesmen, But the OP suggested asking the interviewer. Developer interviews often have multiple rounds with different interviewers, so you get a chance to ask the same question to multiple people. If their answers don't match, beware! :)