I assumed otherwise because they specifically wrote "sharing". Still, I'm not sure agree with:
> requiring them to provide a separate email from the one they registered with completely defeats the purpose of obfuscating the email in the first place
I can't use most apps without providing an email, whether they need it or not. That's a much worse situation than not being able to use some features without providing one (which still assumes me having no access to or knowledge of my own iCloud email).
But if you share a trip to a person who's on Tripit - they just get a notice and a record in their webapp.