Thanks for all for suggestion this great tool Social Proof, we need it really in Website.

Yes, good idea... I think maybe better if it displays before customer purchase like a timed or scroll or cart page pop up that displays the same type of social proof (X units sold) so customer sees it BEFORE they purchase... help move them one step closer to purchase. But nothing to intrusive... a small box on one side or in a corner that displays for a few seconds and then disappears without the user having to click or anything. A good social popup for after the purchase may be to "share" on Facebook.

I already have it through another vendor and it is cheap like 99 a year but it is a coo feature, have had success using it, kind of like the one this company offers https://apps.shopify.com/sales-pop

Thanks, Doug! We've been talking about a feature like this recently. I'll keep you posted :)