Readability and font sizes

Preliminary notes for an article:

What is a ‘good’ font size for reading from a screen?  Lots of variables:

• screen size/resolution
• age/eyesight of viewer
• length of paragraph
• measure of paragraph
• reader’s taste

I’ve always assumed that larger font size = more readable, but having read Vivien’s critique of my website, comments on the iA site and through listening to my work colleagues, I’m not so sure.

Can anyone point to any research on this?

Does the font type (serif vs. sans) have any effect?  I think that Georgia at 16px looks great and reads great, am willing to admit that helvetica/arial (and sans in general) not so much.

Congruence of taste and readability - emotional aspect?

Possible cop out - respect the user’s setting by specifying font-size: 100%, p {font-size: 1em;}.  Except - how many people actually change this setting.  Do you know any normal, non-geek people who do this?  Are there any stats on this?

Any pointers, ideas etc. welcome.