Yep...I'll confess it, I'm a re-user to
I suppose I got it from my penny wise Gran, she has always saved them and re-used them (though like the consensus here I scrap those that held raw meat, seafood, etc). She takes it a step further though, saving re-usable things like tin foil and saran where possible and sanitary.
If I've got a more $ heavy-duty big freezer zip-lock that has stored raw meat, etc...I will sometimes wash it out in super hot soapy water (twice) and then use it to store things like sewing bits and pieces, craft supplies, etc...things that are not edible in other words. (They also handy for packing toiletries in for trips).