Passes allow users to bypass typing a CAPTCHA when posting, as well as ISP/IP range/country blocks. They can be purchased with a debit, credit, prepaid card, or Bitcoin, and purchased as gifts for others.
On an unrelated note, I wrote a pseudo-news post on my blog that explains my rationale for making the decisions I do. For the nerds among us, I also have a post queued up about how much bandwidth will be saved by the migration to our static domain (4cdn.org). Since I hate writing news posts (and writing in general), I'll probably spend more time writing smaller updates here in the coming months.