Group Think is a very effective mechanic used in Group Buying that is perfectly suited for use elsewhere, other than where exclusivity is important of course!
By publishing the number of items that have been sold, consumers are comforted at the prospect of being part of a crowd and are more willing to buy, assured that many others have thought long and hard before deciding to make the purchase negating the need for protracted consideration!
The effectiveness of this this mechanic will peter out when availability concerns emerge, but until that point the strategy is sound.
Where access to specific purchase data is problematic, manually updating the Offer to state “more than 1,000 sold to date” works well…
As well as “number sold”, “people who bought X, bought Y” is an example of Group Think. Again these can be manually programmed where automation is not an option.