Forgot your password?
So you built a super-easy-user-friendly website for community members. But despite all your efforts to make everything go as smooth as possible there is still one thing which remains a bump in the road: logging in. Of course you offer a 'remember me' checkbox and hope your users will let the browser remember the password, but there always will remain a group of users who doesn't use that option, or login on a different computer and... forget their login credentials.
If they use the 'reminder' option to receive a new password, chances are high they'll leave your website if they don't receive the email within 15 seconds. Maybe they wanted to leave a clever comment on a content notification they got, maybe they wanted to place an order. You'll never know.
Some websites choose to avoid this issue by providing a direct login link through email. See the the example below from Hyves (a facebook-like community very popular in the Netherlands). You can login using a link with a unique variable which allows you to login (probably just once and in a certain timeframe).
[caption id="attachment_843" align="alignnone" width="574" caption="Hyves (Dutch Facebook) generates a new login link on some emails"][/caption]
While this might be bad practice and a potentially unsafe/security issue, I think it is user friendly.
Drupal only provides a direct login link when you reset your password into a randomly generated new one. There aren't any modules which would provide this functionality (well there is something remotely like it and also this issue) which doesn't surprise since it isn't "the Drupal way". But still, for sake of argument, it could be a usability improvement.
At least until OpenID becomes mainstream, which will probably take another decade. But then again things might starting moving fast when popular community website become OpenID providers. When sites like Facebook and Hyves become OpenID providers, people kan login on every other site which supports OpenID using those accounts. Which is a good thing.