Random probably idiotic, airhead question but anyway...

can followers of the more religious/spiritual 'idols' totems go Toxic too? All possible totem/idol/patron/etc?

Been reading today on Winternight and their 'Toxic Wolf' spellcasters, so I was wondering if that is/was legal (and if I have just not gotten the info in rules). Something like a psycho Left Hand shivaite or insane St-George fundie is possible?

Power corrupts and magic is the epitomy of power. In other words, yes, everyone has the potential to go twisted and/or toxic. And the road to hell is paved with good intentions.

As Drogos said, it's certainly possible.
I could easily imagine apocalyptic toxics with a warped religious background or a toxic looking to destroy a society perceived as unfaithful.
Probably even a sterilist toxic from a bhuddist background who is looking for more radical ways to cleanse humanity of all mortal desires.

Keep in mind, though, that SR4 distinguishes Toxics from the Twisted Paths.
A holier than thou paladin driven over the edge by religious zeal would be more likely to end up twisted rather than toxic, even though both would be possible.

I would postulate that more organized religions would be more on the lookout for toxic and corrupt leanings, and move to take them out.

who watches the watchmen? we all watch each other.

I would actually say that religion more organized or not does not matter. When mages start becoming toxic there are probably many different ways they start to change if at all. A mage might seem perfectly fine until they completely turn, or they might just drop off the radar and never be herd from again. I would say that a community of mages who continually check up on each other and make sure there are no changes to their magic life or even maybe their home life might have a better chance of finding out a mage is going toxic, but lets face it most people don't constantly poke and prod other people on a constant basis (people still like their personal space.)

Do they 'take them out', or do they use them, vis-a-vis The Devil's Dancing Bear?

Also the occasional slippery-dip and grease patch.