Re: Why are people so against meat from craigslist?
I won't use products with a history I can't confirm, but it's not about poisoning possibilities (in fact, the thought never crossed my mind).
For me, it's about the nutritional content, since my sole reason for feeding raw is to provide my cats with the healthiest foods I can.
There are several vitamins known to be sensitive to light, oxidation, and freezing; with the rate of decay varying with the conditions. There are also indications that other nutrients, including the amino acid Taurine, are sensitive to freezing (among other things). In every case, a defrost and refreeze seriously exacerbates the decay.
Since it's not possible to determine how many times or to what extent craigs-list-sourced products have been frozen, thawed, and re-frozen, I choose not to use them.
It's totally a comfort-level choice.