Premium accounts could work for Pinterest. I think ads will make them a lot more, their model is well suited towards ads. Not to say they couldn't do both.
Yes, I expect ads will make them more on average, but they could certainly make more from me (well... my household) if we could just pay them to remove the ads, and perhaps have some other premium features.
My wife is a normal computer user. A savvy one, but still a normal one. She's a bit behind me on the curve of getting pissed off about ads, but not as far behind me as Pinterest et al might hope. If Pinterest fills up with ads, I'm not sure she'll stay.
Pinterest content is fairly similar to ads. I recall something where the founder described it as digital magazine clippings--I figure that actual magazine clippings were more than likely originally promoting a product.
The way I'm imagining it, the ads could fit in very well. You say you're already using it as your cookbook. If a chicken pays to promote recipes involving chicken, this hasn't really effected your usage in a negative way.
If the execution is good, I'm not sure where the objection is coming from. Of course, the execution could be bad; but you seem to be implying that ads would be very negative either way.
