This is a usability question: could we please use a typeface that is a better fit for screens? Something sans serif would be very welcome.
Even if we allow the users to select a font in their preferences the default font for users upon first visit or for unregistered users should be a sans-serif.
We could try and find a font that suits most people the most, and perhaps we can do better than Quattrocento.
Before we do, I think we should consider just letting everone choose their own font, so please let us know what you think of that suggestion [on this other meta post](/meta?q=56).
I don't think it's a given that "sans serif" is better for screens. There are screen optimized serif and sans-serif fonts, and many of the same benefits of serif fonts for print work such as books apply to body content on the web as well.
It is true that many serif fonts optimized for print do _not_ offer good readability on digital screens, especically at small sizes.
I think the default for body content of posts should actually be a serif font, but one with good screen rendering properties.
I would consider making site Chrome/UI elements sans to diferenciate them from user generated content (posts, comments).
Additionally a user preference would be a welcome change over most sites which force you to use a single upstream choice that is not necessarily the best for all users.