Hmm, I guess I will degrade my account and flickr will lose a paying customer.
Seems like most users either a) are resigned to seeing ads on every website or b) have installed an ad-blocker. I don't see how paying for ad removal can generate much money.
Keep in mind that the ad-free experience also means visitors don't see any ads when browsing your photos if you are a pro user. This may or may not be important to you, but is arguably worth the $25 per year for any use that approaches professional level.
Seems like most users either a) are resigned to seeing ads on every website or b) have installed an ad-blocker. I don't see how paying for ad removal can generate much money.