Empty retail space is the current look for most high streets. Pop-up shops can only fill so many vacant lets. I really like this new idea from RIBA. Multiple Installations combined into a kind of indoor sculpture park -but viewed from the pavement. True this one is not really taking on the empty spaces exclusively. But it did make me think about what would you do if you did co-ordinate all of a shopping centers empty lets into a single piece of shopper engagement
http://bit.ly/kDEVzb - Londonist.com
http://bit.ly/me9jZi - RIBA / Regent Street Project
also seen on http://philipslade.posterous.com duplicate but easyier to use (in a rush) platform