Lets take your arguments gmaxwell, and look at them in the context of this specific proposal.
So the blocktime would be at 5 min in this case. The orphan rate would be higher, but I'm guessing it would it rise by more than 5% or 10%. And lets remember, the orphan rate is under 1% of all blocks, so the actual percentage of orphans would change from lets say 0.80% to something like 0.85%. I'm just making these numbers up, so let me know if you disagree or have better estimates of the actual values. I don't know to much about the convergence concept. I would guess that 500KB blocks every 5 minutes still be well within the margin of safety though.
Good to know. Lets not do that! I don't think anyone would think 5 minutes is stupidly low (unless they were stupid?).
This may be a good point. I don't know enough about how the headers work, but I'll try. Empty-block headers are about 80 bytes. If every block thus far had been empty, we would have ~20MB would of block headers since the genesis. That number would be ~40MB if it had been 5 mins from the start. A question: would the header-of-a-100-transaction-block + the header-of-an-empty-block be the same size as the two 50-transaction headers combined? If that is true, than the added header 'overhead' costs would seem to be reasonable, basically an additional 80 bytes every 10 minutes over what we generate now.
Seems like Meni is taking you up on the security side. Statistics aside, lets not forget the importance of that first confirmation! I've met dozens of people in coffee shops helping them to get some bitcoins. In purely human terms, there is a big difference between 5 and 10 minutes. 5 minutes is fast food, 10 is not. You expect putting gas in a car to take 5 minutes - 10 would be a drag. 5 minutes just feels a lot faster than 10. And since that first confirmation is way, way (maybe 100x?) more secure than an unconfirmed one, everything happening twice as fast would be very convenient for the bitcoin community as it is today. I agree that in the future there will be lots of solutions to these issues, but to get there from here we need to keep people happy and things convenient so that the community lives on.
Of course, if Meni is right, and I think he is, then you can multiply that savings if you need more confirmations. The current security provided by three confirmations (30 mins) could be replaced by four confirmations at 5 minutes (20 mins), and time savings will be afforded at any desired level of security.
It's good there are options, but this is a very technical solution. Don't forget we want to make bitcoin better for even minimally technical users, so therefore it is not an argument against 5 minute blocktime.
The distribution curve doesn't change shape, but the timescale underneath it will be shrunk by a factor of two! Again, transactions where two people initiate the transaction and then wait it out, but that 1, 2 or 6 blocks. Whatever your number is, you will be waiting half as long on average. Adjusting to keep the security level the same would not result in a 50% times savings, but maybe 30%. Meni will tell you the exact amount.
No one wants to wait longer. This is 99% a technical issue, and if the core dev team gives it's blessing, people will be very excited. Why not propose raising it to 20 minutes and see if there is a similar level of excitement. I tend to think we need a hard fork to prove to ourselves that we are dynamic community and can handle the challenge. With core dev support, consensus will easily be over 95%.