In the past the keyword limit at adCenter was about 40-50 thousand keywords per account. But now it has increased to 100,000 keywords per account and 20 ads per order. But the request for 3 account per credit card, which include one or more campaigns and one or more orders, remains unchanged. An email posted in Webmasterworld by a Microsoft adCenter representative says:
At this time, Microsoft adCenter will allow 3 account per credit card, which may include one or more campaigns and one or more orders. The limit for keywords is 100,000.00 and 20 ads per order. You may submit a request to increase the keyword limit. To do this, I will need the following information:
1. Customer name and account number
2. Customer service level (Standard, Select or Premium)
3. Requested limit
4. Business justification for request
Once we have received your request, it will be looked into and will take up to and including 7 business days to complete. You also may create another account using the same credit card. You would then have an additional 3 accounts to use and create additional campaigns and orders. You would still have a keyword limit of 100,000.00 in total for this new account.