If you're asking me specifically, then yes I'd be willing to pay for it, preferably as a part of a set of services/tools (that would need to include imap, contact management, calendaring). I'd happily switch away from Google services for that, providing usability isn't hugely compromised [1]. I'm actually working on open-source infrastructure to get us closer to this [2].
If you're making a general point about why people would pay for such things then privacy/security is just one more axis on which to consider purchasing decisions. It's up to the individual/organisation to decide what they really care about when they're choosing between different options. My concern is that there aren't really enough options that do consider the privacy/security aspect as well as the usability, so I see a gap there. I'd be glad to hear others' opinions on this though.
[1] I was already a paying user of MobileMe purely because I wanted auto-syncing of contacts and calendar so that price-point ($99 per year) is clearly one I'm willing to pay for something that works. I paid it grudgingly at first but I did pay (and renew). Whether that's actually a sustainable price-point for the provider is a different question.
How much are such things worth for paying customers?