The essential difference though is that mobile carriers are less trustworthy than the most trustworthy domain registrars. Plus mobile networks are usually contr

The essential difference though is that mobile carriers are less trustworthy than the most trustworthy domain registrars. Plus mobile networks are usually controlled by a single authority in each country, whereas the Internet and its domain name system is a bit more democratic. It's all relative of course, but still. So given a choice I'd rely on my email address more than "my" phone number.