I didn't bother to send them a reply, I simply deleted all my photos (less than 250) and closed the account. I'm pretty sure they are getting the message. Had they posted "Hey, we need to start charging a few bucks a month" I would have considered staying. As it was, I went with SmugMug, and am real happy with their service so far. Fast and ad free. Yes, I'm paying, but a whole lot less than $399 a year.
I'd be surprised if the executive who came up with PB's strategy is still employed, or that PB doesn't come back with a more reasonable offer of say $5 a month.