There is at least some, if not a lot, of truth to what Loffy has said. The (strongly suspected) core damage in Unit 2 was due to core uncovery due to letting the ONLY running diesel pump run out of fuel. The second core uncovery was due to inadvertently due to not keeping the RCS vent (I assume SRV) open, causing RCS pressure to increase above the diesel pump shut off head. Because the Unit 2 core got damaged, the radiation levels around the plant got much worse, the control room had to be evacuated, etc. Prior to this damage, it appears the units were relatively accessible (especially, 2, 4, 5, and 6).
It does not appear that fire hoses were prestaged to the SFPs once the extent of the loss of power became known. Had such hoses been run, it would have been relatively simple to get water into those SFPs.
Part of the issue is that detailed information (what is broken, what is flooded, what was washed away) has not been released. I know in our Emergency Response drills, there is a great deal of emphasis given to keeping the news media, INPO, etc updated. This update includes much more detail than what has come out to date.
Yes it would be difficult to transport a diesel that could run an ECCS pump. However, one big enough to run a pump equivalent to a CRD hydraulic pump or a standby liquid control pump is probably possible, as would one or more to run the equipment associated with the normal fuel pool cooling system and its heat removal system (if that system is still intact, which is unknown).
Once the first secondary containment blew out, or hydrogen got detected in the secondary containment, why weren't panels taken off the remaining units to allow crossflow to vent any hydrogen?
Look at this picture from yesterday, from before the Unit 2 core damage occurred. While they may be too small to see, there does not seem to be a huge amount of portable equipment staged near any unit.
http://www.digitalglobe.com/downloads/featured_images/japan_earthquaketsu_fukushima_daiichi_march14_2011_dg.jpgThe above does definitely NOT mean the people fighting this disaster at the plant are not heros, working in unbelievably difficult situations with severe concerns about their family and friends. It does mean that, based on what little we can find out from far away, there does not seem to to have been a huge mobilzation in day one or two to mitigate the event.