I tend to regularly check and purge my Gmail Spam folder to make sure nothing goes through by mistake and have noticed some legitimate emails that did: in particular from LinkedIn and my alumni association.
I repeatedly marked them as "not phishing" and "not spam", even added the incoming address in my address book to no avail: they are still going to spam.
So, just a heads-up.
I'm very happy with my paid spam filter service (SpamStopsHere.com) which reduces the false positive rate, possibly at letting slightly more spam through -- but that's how I'd like to prioritize it.
I wrote about it a few years ago: http://normalkid.com/2007/08/21/my-spam-solution/
(Also, I get an absurd amount of spam. My MacRumors address gets 400,000-500,000 spam emails a day, which are blocked.)
A weeks or so before xmas our main domain went dead and took 6hours for most users and up to 24+ for others to be able to access the site again. We provide an on line SaaS solution to schools so luckily it was almost the holidays; things could have been much worse.