Sponsor is perhaps a strong word. You need another WeChat user to verify your account by scanning a QR code displayed on your app using their app. You need to do this when you create an account, and also if you haven't used your account in a while. I assume this is some sort of anti-spam/anti-bot feature.

Note that the above is just for the chat feature. You have to jump through more hoops if you want to make payments using the app.