#1 - March 28, 2012, 11:40 a.m.
http://www.google.com/moderator/#16/e=1fb501
It is pretty simple. Everyone can vote and comment on ideas and submit their own ideas for others to vote on. The ideas are ranked by their popularity. Of cause Blizzard isn't bound to this list, but maybe it helps them to spend the little time they have for the BCP-API the most efficent.
Current top 10 (30.03.2012):
x. (pro/con) topic/description
1. (12/0) Enchant information
2. (8/1) Itemset Information (set name, set item names and set bonuses)
3. (7/1) Reforge information (mapping id to reforged stats)
4. (7/1) List of sold auctions
5. (7/1) Identification token for identifing character owners
6. (5/1) Information about mobs (name, zone, etc.)
7. (5/1) Updating BCP-API documentation
8. (6/2) Additional information about misc spells on item ("Equip", "Use", ...)
9. (6/2) Diablo 3 API (currently planned for a future release)
10.(6/3) Starcraft 2 API
Update: Clarified "BCP-API". Thought that it was an common abbreviation.
Update: Added current Top 10