Hybrids to Plug-Ins: Not as good as it might sound?

We have heard about this before here and here. Yesterday's Times also has an article about converting hybrids to plug-ins.

But the idea of making hybrid cars that have the option of being plugged in is supported by a diverse group of interests, from neoconservatives who support greater fuel efficiency to utilities salivating at the chance to supplant oil with electricity. If you were able to plug a hybrid in overnight, you could potentially use a lot less gas by cruising for long stretches on battery power only. But unlike purely electric cars, which take hours to charge and need frequent recharging, you would not have to plug in if you did not want to.
..."If you're thinking about this as an environmental issue first and foremost, you're missing the point," Mr. Gaffney said. Curbing dependence on foreign oil, he added, "is a national security emergency."

This quote sums up what may be a problem with plug-ins, but by all means not the only one. Plug-in may seem attractive from the point of view of reducing oil use from transportation sector, but it will increase the electricity usage which in the US (and the world) is predominantly coal based. Prof. Andy Frank of UC Davis is a big supporter of plug-ins and he claims that on a well-to-wheels basis, plug-ins will be responsbile for less CO2 emissions per mile travelled. I am not sure that this claim holds up in all possible mix of electricity in the US grid. In addition, if plug-ins were to become significant in number (lets say 10% or more), then the effect on grid management would be very different, and in some if not all cases, plug-ins may be responsible for the tail of the demand curve causing a price spike in the electricity spot markets. Thus for plug-ins to make a meaningful contribution, we first must have a cleaner and more efficiently functioning power sector than what we have today.
Some of the other commonly cited problems with the plug-ins are the same as that of other electric vehicles, i.e. weight of the batteries and the range they can offer on all electric mode. Never the less, I am sure that there will always be enthusiastic people who will keep the Plug-in path towards electric vehicle alive, and that I do not consider a bad choice at all.