Also known as a neat trick you can try out on hobby/free apps but are most likely horribly inappropriate for the average startup. As soon as you get even remotely serious, for example spending money on marketing, you're going to wish you captured email addresses up front. When you're spending money on customer acquisition, "cool, 10,000 people tried our app" doesn't mean nearly as much as "cool, we have 2000 email addresses".
> As soon as you get even remotely serious, for example spending money on marketing, you're going to wish you captured email addresses up front.
Just to add a dissenting view, I am ruthless when it comes to who gets (or, usually, doesn't get) my e-mail address.
If you require one at any stage before I am ready to commit to your company, you will almost certainly lose me as a customer forever.
If you take one and ever use it for anything other than the explicit purpose for which I gave it, including sending unrequested marketing spam, you will almost certainly lose me as a customer forever the first time I receive such a message. You will certainly get killfiled so you can't reach me again in future.
The only exceptions are likely to be established companies with which I have some sort of history, if they are sending something that might be genuinely interesting, e.g., when Amazon started sending out recommendations e-mails and gave a clear way to opt out right from the start. If you are a start-up, it is highly unlikely that you will be in this category, however.
[edit] We have an email alert feature on our job board platform, that allows job-seekers to get email notifications for new job ads. Standard functionality. When we removed the registration barrier from this user journey (so it's now just a single text field and submit button), email alert creation rates basically doubled on most client sites.
Also known as a neat trick you can try out on hobby/free apps but are most likely horribly inappropriate for the average startup. As soon as you get even remotely serious, for example spending money on marketing, you're going to wish you captured email addresses up front. When you're spending money on customer acquisition, "cool, 10,000 people tried our app" doesn't mean nearly as much as "cool, we have 2000 email addresses".