With an on-site "Contact Support" form, you can at least compare their IP address with historical login addresses. But that comes with its own weird problems like, for example, a sibling claiming their brother's account from the same household to read their juicy PMs or steal their credits or whatever. Or giving moderators access to more sensitive information and power than necessary.

Password reset being "optional" just means that people are going to use your support system for it when they eventually forget their password or the initial registration session expires. Reddit and HN have optional email while your new website's only user just forgot their password without an email address on file. What are you going to do when they ask for help off site?

And by the time you're fielding SMS and Twitter handle password resets, you may wonder why you didn't just put more emphasis on the email address input field. Now you're polishing your SMS or Twitter handle reset system that has far more narrow appeal/usage than an email system.

Of course, at the end of the day, it depends on the type of service you're operating. But "make email optional" is a trade-off, not universally good advice. Spend too much time in the HN echo chamber and you'll just do things that work against your users.

People can opt out via http://10minutemail.com/.