I've also learned this just recently: It should be 8MB (with corrected calculations), and DDoS isn't really possible at that block size. If I'm correct Luke (?) and Maxwell said that because of the increase they would not be able to run nodes anymore due to their internet. They've concluded from this that the majority won't be able to run nodes either. This is also wrong. There are plenty of places that offer sufficient internet speeds for 8MB blocks. Although their argument is also invalid due to the progressing block size. We might hit 8(originally 20)MB blocks in 2016, or in 2026/2xxx. Nobody can really know when.
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However I do not see much wrong in increasing the block size to let's say 4MB. That would be some sort of compromise for Gavin and the other developers which would also give the whole network more time for better solutions.
Finally some common sense! Gavin needs to admit and push the 8MB blocks and Maxwell must let go of the centralization fear and accept that Bitcoin can run ok for now with less than 5k nodes. Consensus achieved! I hope the involved parties are reading this or they are notified somehow. I would like to hear their opinion on this.