Not too sure about Thumbtack, but Home Advisor basically just buys Google Ads to get consumer traffic, then turns around and sells the lead to contractors at a higher rate. If contractors spent 20 minutes figuring out how to set up a Google Ad campaign, they could easily outbid Home Advisor for the exact same customer. I feel like this is pretty much the same thing Thumbtack does, with a few logistical differences. These business models really seem unsustainable (or rather uncompetitive) with any service professional that takes his or her business seriously and doesn't mind putting in the work to market themselves. These companies are basically playing Google Ad arbitrage.