It's funny that you say that, because based on (admittedly half year old) data that an app developer collected about reconnect rates, Japan was by an order of magnitude the worst country with regards to number of reconnects that this app had to perform (DoCoMo was the second-to-worst carrier around the world).
Reconnects happen because the cell carrier closes a connection or times out--a good cell carrier won't change your IP address or RST your connections when you switch towers, but a bad one might decide to assign a new IP address each time. On some apps, reconnection may consume up to 1MB of bandwidth each time as they attempts to resync data (Yes, good apps shouldn't do this, but I have seen it happen.)
The problem is not Android -- the problem is the shitty QoS that most mobile carriers put on their networks, combined with the fact that they often kill connections at the NAT layer without notification, time out connections over unwanted ports and block protocols that they don't like.
The end result is that everything on a cell network has to happen over port 80 or port 443, with the SSL negotiation overhead that involves, combined with sending keepalives every 4 minutes. Yes, Android is unoptimized. DoCoMo might be doing everything right, but they bear the price of all of the terrible cell carriers that go out of their way to block data (AT&T, T-Mobile, I'm looking at you). Android 4.0 has a Data usage monitor that helps a ton in debugging misbehaving apps, but data is a fact of life.
That said, Apple may have made a good decision by forcing app developers to use push notifications when the app is in the background. Android messed up push notifications by tying them to Google Talk and Android Market -- this means apps that require push will not run on a large fraction of android devices around the world (including the Kindle Fire). The result is that apps don't use push and implement their own (often buggy/wasteful) push system.
Finally, if DoCoMo doesn't want users to send/receive data, then limit their bandwidth for crying out loud. Don't whine when you provide fast service and people use it. What is complaining to the OS manufacturer going to do? They provide a platform, not the apps or the service they run on.