Picked up an investment from Mark much along these lines. I had a product to show off, knew there was a chance he'd be interested, and rather spontaneously sent him an email. If he finds something about what you've said intriguing, he really does get back to you amazingly fast.
He doesn't beat around the bush, so if you email him, make sure you know what you're looking for. I made the mistake of not having a number in mind, and while it didn't ruin the process, it certainly could have. He also won't read everything in a long email, so don't waste his time or yours, definitely keep it short and to the point.
I've found he's a really great business partner. He makes himself available (by email) at all times, responds quickly, is always interested in finding new ways to promote your business (he networks his investments where he can), and he's a patient investor.