part of this is easy for me because I still don't shop online
the majority of my purchases are still made at small local independent shops - even veggies mostly come from tiny local markets - I buy what they have.
the exception is clothing - I do use local online swaps for clothing. I recently exchanged 8 subway tokens for a Lands End squall coat I was after. The coat is $325 Cdn + shipping + duty online . $25 in tokens was an excellent deal. Best part - the coat is one year old - and has features lost in the recent redesign of the coat. The woman selling it dry cleaned it before putting it up for swap. Based on the condition, she can't have worn it more than 3 or 4 times.
I do use yelp for meals/services. It's helpful for meals - I look at people who have similar views pro/con of places I've reviewed and follow them. It's paid off in all sorts of random ways, including an invitation to a magician's jam/party in Manhattan. It's also led to some amazing meals and food festivals.
Balance eh. I still trust my purchasing instincts most.
edit : can openers. I tend to use the OXO good grips line of kitchen stuff as my hands are occasionally arthritis grumpy during bad weather. I learned about them in an online cooking group.