If an adept has the power, found in an on-line book, called "Face Anonymous" which is simply a power that makes it hard to describe the adept because he looks so plain. Can that power, or for that matter any power, be turned off for a while?

It looks like the rules allude that an adept's powers stay on all the time. But, being a noob, I am not sure.

That's been the subject of much debate. In our group, we allow the turning off of powers like Improved Reflexes, Killing Hands, and the like. Just because you CAN run as fast as bullet train and kill someone with a single blow doesn't mean you always HAVE to. If the Face Anonymous power comes from the Adept Handybook, as I suspect it does, it's not really canon anyway, so it should be up to the GM.

It's usually accepted that you can forcibly turn off powers. Look at Death Trance, you turn it on, you turn it off.

An adept can only have a number of active power points equal to or less than his magic rating at any given time. However, using the 20 karma per point rule, an adept can have a total number of power points grater than his magic rating.

The only way to reconsile these is to say that powers can be turned on and off and only (magic rating) or leff points worth of powers can be turned on at any given time.

Actually, according to the FAQ (italics mine):

SR3 allows adepts to purchase additional power points at a cost of 20 Good Karma points each. Does this mean that an adept can have more power points than his Magic attribute? Or does the purchased power point increase the adept's Magic? Can purchased power points be lost due to Magic loss? What happens if the adept's Magic is reduced to 0, but he still has powers left?
Adepts who purchase power points with Karma do not get an extra Magic point with that power point. You only get that with initiation.
The power point for Karma rule was specifically included for players who do not use the advanced magic (initiation) rules. It is recommended that this rule be ignored if the initation rules in Magic in the Shadows are also being used. Any extra power points purchased with Karma do not count against the character's limit of (Magic attribute) number of power points.
When an adept loses Magic, he chooses which powers are lost; powers bought with Karma can be chosen instead of others. If an adept's Magic reaches 0, the adept loses all magical ability, period.

Instead of that, I'd look at Magic in the Shadows. The mana warp section, specifically. Odd place for an example, yes, but we're all used to that in SR books by now, right?

Anyway, the example text on page 86 mentions the effects of a mana warp on an adept. The adept in the example has her magic rating reduced to 2 and is forced to choose which powers are active, suggesting that the less helpful ones could be turned off.

Plus, it could be argued that if powers can't be turned off, then any adept who buys Astral Perception is always perceiving. Which would mean taking a +2 penalty on all purely physical actions, lighting himself up astrally, leaving himself open to spirit attacks, and more or less commiting suicide by entering a mana warp. Which is a great set of penalties to buy for only the cost of a Wired 1 equivalent.

I've always held the belief that Adepts can willingly choose when they wish to apply their powers and when not to. For example, it's clear that an Adept does NOT have to do phsyical damage in unarmed combat even though he has the Killing Hands power. Neither is an Adept screwed because he has 3 or 4 or 5 Improved (hearing) Senses - he can choose which one is active and which are not.

It's a reflection in my games of the "superiority" of man over machine.

Thank you for the wonderful replies. Not only did you answer my question, but you also pointed out something I missed where you can only have as many power points active as you have magic rating. That makes sense since adepts can gain powerpoints using Karma, which I thought was unfair to mages, but now powers are a lot like spells.

And, yes, that power comes from the Adept Handybook.

I think I will play it so an adept can switch between powers bought with karma, but can only have powers active that total upto, but don't go over, their magic rating. If an adept much change powers in combat, it would be a complex action just like casting a spell.