I would be questioning if people without an email address are actually going to be interested in using anything I am building. In most cases I would imagine not (but my company's target market is 18-25 year old europeans).
Rather than imagine, you should probably do some market testing. Here's a single data point to get you started: last time I talked to a late-teenage member of my family about email, they called it "old", and weren't even sure what their address was.
