This is a recommendation. There is a couple that made an extension for mTurk that is great.
You can find it here:
You must use Firefox browser to use it.
The extension once added, gives you the ability to find out more about requestors. You will see a down arrow next to the requestor name, which gives you how other mTurker's have had experiences with the requestor. Check it out. I love it. And have added my own reviews as well.