OTC-BB isn't the same thing as the Pink Sheets. OTC-BB stocks stocks must register with SEC, unlisted securities do not. The pink sheets are simply a centralized third party which maintains a list of independent brokers and the unlisted securities they trade. Note it isn't a requirement for an unlisted security to be on the pink sheets. Think of pinksheets as like a digital phonebook of brokers. Say you want shares of unlisted security xyz. Your broker can use the pinksheets to find that broker abc has shares of xyz (it may be the only broker in the world that does). Your broker can then buy shares from broker xyz and simply assign them in your account. Remember only broker dealers can trade in unlisted securities.
Pink sheets and OTCBB are the same thing. They are competitors.
The exemptions are very strict and your Regulation D exempt stock will have a restrictive legend on it that does not allow free trading (meaning no pink sheets).
Reg D BTW doesn't relate (directly) to what securities broker dealers can TRADE. It deals with the issuance (i.e. selling new shares) of securities. While GLBSE did multiple things normally these are separate actions. Reg D deals with the legality of a company issuing new securities. Broker dealers are required to trade unlisted securities.
Edited for clarity.
You do not need a broker-dealer or market maker. You need a Transfer Agent. Let's be completely clear -- a broker-dealer is not required.