I was wondering if anyone has tried running one more screen off their MacBooks by closing the lid of the MacBook. This is a common practice of many Windows laptops that support only 2 screens but have multiple video outputs. Since this is a hardware limitation of the number of video out ports and the number of screens that the video card in the laptop supports I would assume that any these combinations should work, if not in OS X but in Windows under Boot Camp at least.
Retina MacBook Pro: Supports two screens through any combination of HDMI and Thunderbolt/DisplayPort; lid closed: three screens though the same any combination of the video out ports.
MacBook/MacBook Pro 13"/MacBook Air/MacBook Pro 2012 (non-retina): Supports only one external screen with the internal one on, but when lid closed should be able to connect one more Thunderbolt display.
MacBook Pro (Before 2012 edition with Thunderbolt and AMD graphics): Two Thunderbolt screens connected with the lid open; lid closed, three Thunderbolt screens. This possibly may not work because of bandwidth limitation of Thunderbolt, not that the video card can't handle it.
Clarification: The configurations I list are what should happen if my hypothesis is true. I am asking for people to confirm this by using thir own MacBooks since I do not own this hardware to test.