Shopping online is easier in some ways than shopping at brick and mortar stores, and more difficult in some ways. It's easier in the sense that you have lots of selection, and comparison shopping is as simple as clicking your mouse. You can shop in your jammies from the comfort of your couch, order and in a couple of days a package arrives at your doorstep. You also save a lot of gasoline, since you don't have to go driving long distances to shop.
On the other side of the equation, unless you've seen the fabric, you don't know what it feels like until you get it, and due to monitor and picture differences, you aren't actually sure of the colors.
That's why good online shops will try their best to give you good color information, and will send you small samples if you ask. I'd rather send you a sample than have you return something that doesn't work for you. Additionally, a lot of online shops will match fabrics for you if you ask them to and will give color advice. You can send them a sample and ask them to match it for you with blenders or other fabrics.
One other point needs to be made -- the issue of "keeping your money in the community" is pretty much a non-issue. Someone posted earlier that if you spend your money locally, some enormous percentage stays there. That's just not true anymore, unless the fabric is made right in the community, and it's not. First, over half of what you spend on fabric goes to pay for the fabric, more if it's on sale. Then there's heat, lights and utilities for the store -- in most communities that money goes someplace else. Advertising and printing of catalogs and flyers takes a share -- those are most likely done in another community. And so it goes. No matter if you shop online, or at your local store, a big majority of the money you spend is going to be sent away, either way.
And as Nan said earlier, most online shops, with the exception of the biggies like fabric.com (a subsidiary of Amazon) are small mom and pop shops just like your local quilt shop probably is.