From user perspective having several sign-in options is a source of confusion: first day I sign in with Facebook... next day I come in and don't remember which service I've used to sign in with? And this time I try Twitter only to see none of my data.
How do you guys solve that problem? I think, this might be even the bigger problem than having 20% or 30% "drop out" on sign up process.
You'll probably see that you don't have an account registered with the website through Twitter, not "none of my data". As a user, if you like FB more, you'll likely try FB login first. If you like Twitter more, you'll likely try Twitter login first (if available).
With single device - you're right... but this becomes really a problem when you expect your customers to use multiple devices: computers at home, at work, smartphone, iPad...
how would you suggest your customer which login to use the first time she tries to sign in on another device?
Would that be my personal email account, my gmail account, my other gmail account, my university/alumni address, my work email or the other work email?
How do you guys solve that problem? I think, this might be even the bigger problem than having 20% or 30% "drop out" on sign up process.