I posted this earlier at Worpress.com and was advised to come here.
I've just come across an organisation which won't commission a Worpress based site because they're under the impression that it has 'security issues' and is vulnerable to hackers. To my mind, any website (and anything which can be accessed via a username and password, like all FTP sites) is vulnerable to hackers and the only serious hacks I've come across have related to non WordPress sites. But I'd be really interested to hear how you'd respond to this organisation.
A support person at worpress.com suggested looking at http://wordpress.com/vip-hosting/ but as this is for users with > 500K impressions a month and costs $500 a month plus a $600 set up fee it certainly isn't for me!