These are the Bing AdCenter limits sent to me by our rep:
AdCenter Component Limits
- 100 accounts per customer
- 10,000 campaigns per account
- 10,000 ad groups per campaign
- 20 ads per ad group
- 10,000 keywords per ad group
Negative Keyword Limits
- Campaign and ad group level: Each negative keyword can contain up to 100 characters, and the entire list can be up to 10,000 negative keywords total.
- Keyword level: Each negative keyword can contain up to 100 characters, and the entire list can contain up to 1,024 characters, including commas.
255 targets per campaign or ad group (255 is the limit for all combined targeting settings which include Geographic, Day of Week, Hours of Day, Demographic, Device)
Site Exclusion Limits
500 sites for each campaign and ad group