How dangerous is it to refreeze meat that has been thawed? I've often been told by people that I shouldn't refreeze meat (particularly hamburger meat) once it has been thawed.  However, this seems a little silly to me.  I can't imagine how meat that hasn't been bought fresh and local could find its way to my kitchen with out thawing and being refrozen a couple of times.  How much damage can one more thawing and refreezing really do?  Can it really be that dangerous disease wise? Or is this just one of those urban myths?
In theory you could thaw and refreeze as many times as you like, though the changes in temperature would definitely alter the quality of the meat's taste and texture.

What matters most is how long the meat has been in the so-called "danger zone" speaking from a temperature perspective. The "danger zone" is defined as being between 41 to 135 °F (5 to 57 °C).

Here is an excerpt from The Professional Chef, by the Culinary Institute of America:


  Foods left in the danger zone for a period longer than four hours are considered adulterated. Additionally, one should be fully aware that the four-hour period is cumulative, meaning that the meter starts running again every time the food enters the danger zone. Therefore, once the four-hour period has been exceeded, heating, cooling, or any other cooking method cannot recover foods.