no, youre right Jim, i think it does go without saying that user care is paramount, BUT, most users dont know or understand in the first place and I dont mean that in a bad way, but everyone cant know everything. The tricks used to get virus's onto a PC are very advanced these days, very clever, and working in IT I see it daily almost, where people have fallen pray to these things.
good AV is important, and generally most AV apps do a good job BUT they are designed for general protection. They are designed to protect people against simple attacks or infections. They arent designed for people who are going to surf porn sites or dodgy software download sites, if you do that, you have to take extra precautions such as better software, user account control ,or have your wits about you!
but, for the purpose of this thread, everybodies suggestion is perfectly adequate, as I said previously, its down to personal preference, so, visit each AV site individually and see what it offers and pick one.
As a side note, I find MSE to use the least resources, but it ties in nicely with the MIcrosoft OS BUT be very aware that there are trojans/virus's out there that now mimic MSE, AVG etc....so learn your software!