This is Peerflix (DVD sharing) meets a clothing swap. Similar to how Peerflix used to work, items are exchanged through the mail. In this case, you exchange items using prepaid envelopes you buy from the company, $12.50 for three. Unfortunately, Peerflix didn't stay in business. Let's hope thredUP makes a better go of it. The fact that they won't be facing a dramatic technology transition like Peerflix did from DVDs to streaming video may give them a better chance.
Here's the surprise, at least to me since women made up the majority of every clothing swap I've attended. This company was founded by three guys. I do appreciate their data driven approach. A short tutorial I took on the site estimated I had $700 worth of clothes that I'm not using that I could replace with fresh new-to-me threads for $200. An impressive ROI, but not sure I want to turn my closet into a mini-distribution center just yet.