> I suspect the fact they make so much revenue from advertising has actually blown tepid at the efforts to seek revenue elsewhere

I'm not sure it has -- I think (certainly this is true of the most recent quarter, but I think its a longer term trend) non-advertising revenue is growing at a faster rate (% increase/unit time) than advertising revenue. Its just that the fact that advertising revenue is so much bigger to start with makes the increase in non-advertising revenue seem insignificant in relation to overall revenue.