Its completely ridicoulous. I'd like to see the percentage of people which use a web-based email service as their primary address, I'm sure it's like 60%.
I use a web-based email service (gmail) and have it set up as the default mail client. Meaning those annoying mailto links don't open up outlook. It's a slight improvement, but it's still very obnoxious. Even if I do want to send somebody an email from a mailto link I will copy and paste the address.