I have had problems (with Netgear DG834's specifically) where they seem to suffer problems when only powered occasionally.
A perfect case example is my Girlfriends father who as a Health and Safety Consultant seems to like to unplug everything at night. He has been through a few 834's now and the symptoms in each case seem to revolve around the device not being able to connect when first being powered up.
In short devices like that are designed to be powered up on a 24/7 basis and you may get unexpected results or shortened life if you only power it on demand.
In my household I have fought the green argument several times, usually by one of the following (dubious) arguments
1. Replacing all the lightbulbs in the house with low energy ones, this results in a net energy saving that is more than equal to the energy costs of leaving my equipment powered.
2. Insistence that in some cases power cycling shortens equipment life, in some cases the energy resources that went into the initial production of this equipment can be more than it will consume in it's design lifetime therefore the total energy cost of the equipment is only improved by leaving it powered up.
3. Nearly all of the energy that goes into my computer is turned into heat (ignoring the minimal energy required to keep the fans and hard drive spinning) this in turn means that I have never had to turn the radiator on in my study, which in turn lowers the energy we consume to heat the house. (ok this one is tenuous at best and is a moot point in the summer when I am opening windows to get rid of said heat)
ooh and the best one, my business now operates through SIP phones, my home extension will only work if the router is powered :-)