That sort of thing does really irritate me - I've had it just this week on AW. They are the ones [supposedly] looking for work, so unless you've got atrocious feedback then why - if they're genuine - wouldn't you at least get a reply?! Though maybe give it a little while - I often, even on work email, read messages yet don't have time to compose a reply till later.
(Pity - they otherwise look pretty hot!)
