I'm an equal opportunity shopper! My LEAST likely places to shop are the big box stores. If that's what others want to do, that's their choice. Fabric selection at local WM is very limited, and when I wanted some of a licensed fleece they had a couple years ago, it took about half an hour to get somebody to come and cut. I do think J's is making an attempt to improve their overall quality, but they've also raised prices significantly.
An example of online shopping I love is Missouri Star's Daily Deal! No, it's not supporting MY local economy, but it's still part of the quilting industry, and I think what Jenny Doan and her family have done for their town and the surrounding area is fantastic.
I posted a fairly lengthy response on the other thread regarding some of the shops that I go to locally. If I'm looking for a specific line, I'm more likely to look online than to drive 30 miles to a shop. If I am looking for something more general, I'll head to the Mennonite shops.
I've NEVER seen fabric at thrift shops. I have bought lots of men's dress shirts, inspired by Bonnie Hunter, at both thrift shops and rummage sales. Last week I bought 9 at a rummage sale for 50¢ each. I also bought some at Good Will that ranged from $2.99 to $5.99. I go for long sleeve in the larger sizes if at all possible, unless it's something really unique. A friend and I are swapping; she is making Scrappy Mountain Majesties and I am getting ready for retirement!