Ask HN: Launching soon email capture – anyone using Twitter as an alternative?

Instead of the standard Mailchimp/LaunchRock 'launching soon' email capture form, we're considering using Twitter as a substitute (e.g. 'Stay up to date on our launch by following us on Twitter' vs 'Enter your email and we'll let you know when we've launched').

Anyone have any experience doing the same? Metrics, anecdotes, opinions are all welcome.

We know our target launch market user is also likely to be a Twitter user, and we're OK with limiting our reach at launch to Twitter users. Our only concern is that the notifications will get lost in the firehose for users with large following counts.

Thanks HN!