Turnover is the effect of one of a number of causes, and not all of them are indications of bad management or a bad company.

It's possible the organization encourages people not to linger in the sense Alex Papadimoulis discusses in http://thedailywtf.com/articles/up-or-out-solving-the-it-tur...

Of course, getting the why of a turnover rate is hard; an employer with a culture that encourages negative turnover probably won't be willing to fess up. That probably involves contacting enough former employees to get a non-biased sample, and convincing each of them to be honest. That is, if they are willing to talk to you at all.