Invitations have been re-enabled under a new, dynamic system. The dynamic system adjusts the number of invitations you receive based on the quality of the people you have invited in the past. That's all you really need to know. But if you're interested in the nuts and bolts of the system, read on.

Details

There are two things to keep in mind in the new system: Your personal cap and your class cap. Power Users and above receive 1 invite every 15 days (every 10 days in the case of Elite VIPs), up to either your personal cap and your class cap, whichever is lower of the two.

Personal cap: Power Users and above are assigned a dynamic personal invite cap based on the performance of their past invitees. The exact details of this cap are are not made publicly available to keep people from gaming the system. However, if you invite good members and help them to get on their feet then you'll earn a higher personal cap.

Class cap: Your class cap is entirely determined by your userclass. These values may change over time at the discretion of the staff, but are otherwise steady. These values do not change based on the performance of your invitees.

The class caps are as follows:
Power User: 3
Elite User: 5
VIP: 10
Elite VIP: 15
Honored Members have unlimited invites.

FAQ

Q. I've just been promoted to Power User. How many invites am I allowed?
A. Until you've invited 3 people, you will have a cap of 1. After that, the dynamic system will begin to evaluate your past invitees and assign you an appropriate cap.

Q. Why do I only have 1 invite when I used to have 10?
A. All invites were been reset to 0 when the new system was put in place in order to allow the new system to populate invites naturally.

Q. Is it possible to lose my invite privileges?
A. Yes, if you frequently invite poor users, you can lose your inviting privileges completely. However, you can still forward people to #bginvites on irc.bitgamer.com to get an invite from a dedicated group of volunteers and staff who frequent the channel.