Which option do you choose to login

  > And what if it's something you need to use
  > once in while? Why a throwaway email address?

Then I use it once in a while, but I'm prepared to abandon the email address. "Throw away" doesn't mean that I use it once and can't use it again. If I find that the service is useful and trustworthy then I continue to use that address and promote it into full service.

  >> "I don't trust Twitter"

  > You don't try, or you just leave after finding
  > out that the app can follow/post tweets?

I don't understand your question, but I'll try to guess at what you might mean. To put it simply, I don't trust Twitter, nor apps that insist that use Twitter as an authentication method. They end up being able to post as me, or read my tweets, or read my DMs, or whatever. I won't allow that, and I don't have time to chase down what they may or may not do.

A throw away address for agreatservice.com would be "agreatservice@somedomainIown.com".

If it's something that I clearly have a semi-ongoing use for, I use gmail - it's my throw away address for general web access...MOOC's for example.

That said, if I click a link on HN and it requires an email to try out, then I almost always hit the backspace key because the purpose of the app is to collect email addresses not do whatever it purports to do.

Did you ever notice that HN does not require an email?

Yes, it is kind of tiring.

Even if the app asks only to fetch basic information, I think that I shouldn't go through them (Facebook, Google, Twitter) to assert my identity, since I don't pay any of these companies for this service, I can't trust them to keep my best interests in mind.

I feel that there should be a way for me to be my own identity provider, and email has been the closest I've got to it.