[Evbn]

It is a protection against typos, because people are lazy and error-prone and it matters because getting it wrong means email delivery fails, whereas a misspelled name is no big deal.

So, elegantly, two different issues use the same simple solution.

[nostrademons]

It's not elegant at all - it makes the user do extra work at signup. Wasn't there an interesting blog post on HN about 5 years ago that showed that each additional field you add to the registration form cuts sign-ups in half?

The better solution is to send an e-mail with a confirmation link upon signup. This also protects against deliberately falsified e-mails, and against typing it incorrectly twice, and against folks who automatically copy & paste when they see "Confirm your..." And it's only a tab switch and click rather than having to key in a few dozen characters, which matters even more in the brave new mobile/tablet world.

[lucaspiller]

I believe that extra field thing is correct. However I don't think your solution is really great either, by forcing the user to confirm their email before continuing your are interrupting their flow. In some cases when I've had this and the email has been delayed by even a few minutes I haven't bothered coming back.

Edit: Sorry I kind of misread your comment, but what I said is half relavent. None of the protections you state you get without forcing them to click the link before continuing.

[nostrademons]

Yeah, confirmation e-mails suck from a UX perspective. However, they don't gratuitously suck - they solve the problem they're trying to solve, and often users can tell why they're necessary. Extra form fields suck from a UX perspective and have the added problem of not actually solving the problem they're trying to solve.