Redfin makes money by helping people buy homes. They also sell homes and advertise a 1 or 1.5% listing free depending on which geographic market. Sounds like the type of good deal you hear about in other countries [wsj link] or at Surefield!
But you need to read the fine print. They forgot to include the buyers agent commission of 3%!
So that just adds up a total cost to sell your house of 4 to 4.5% which is not that big of a discount after all compared to the normal commissions.
Redfin goes on to brag about their sale to list ratio and how they sell homes for more than they list them. But that is circular logic since the listing price is always arbitrary derived-- what is actually going on is that they are underpricing their homes in order to sell them more quickly with less work (link to other).