Many condominium and homeowner associations have significant  architectural restrictions, including some restrictions and requirements on exterior lighting.  Common element lights, as well as decorative lighting for units, lots, and limited common elements that are installed by unit owners, are becoming more and more common.  The following article from HOAleader discusses some important issues related to lighting restrictions:

http://www.hoaleader.com/public/Does-Your-HOA-Restrict-Lighting-Should-It.cfm