Here is what I have been told.
Leaving the battery in slowly cycles that battery. So for me, I have 180 Full-Empty charge cycles under my applecare warranty, and 300 before the battery gets to "80% original capacity". On my battery, usually accumulate about 4 cycles a month if it is only plugged in. Also, leaving the battery in and plugged in all the time messes with the micro processor inside and will make it charge less while saying the battery is full, hence you get 100% charge displayed but less actual charge. Now, it takes about 3 weeks to a month before the micro processor starts to get out of wack, so what I have been told to do on my mac and on my Asus is to, assuming it has been mostly plugged in on my desk, unplug it and use it until it goes to sleep from lack of battery power. Now, wait 4-6 hours, press the power button a couple times in that time so that it gets all the electricity out. Then, plug it in, and let it fully charge, while keeping it off. Then turn on and start the count down for another 3-4 weeks.
I cannot help you with the matter of yanking the battery out though, I do not imagine though that it is any worse for the computer than the power going out when a tower is plugged in.