The secret to using pop3 is to make sure your email client is set to delete email off the server after it has downloaded. If you down't have a local store of your email, it also makes it more difficult to move provider, and if their servers lose your old email, you may not have another local copy. And yes email providers have lost customer emails before. Having a hacked email account is another risk, if a hacker gets into your online email store, they potentially have access to many peoples lives, and there is the risk of identity theft.
That's the "secret" but the reality is many people these days want email access via multiple platforums (email program / webmail / mobile phone). POP3 isn't designed for that, and I've also never been a fan of IMAP either.
When there are so many low cost or even free EAS / ActiveSync providers around I dion't know why anybody uses anything else for email these days.