Buried in last night’s update on skyrocketing mobile usage, Twitter CEO Evan Williams revealed that the company now has more than 145 million registered users.

The last time Twitter went on the record with member registrations, it was touting 105 million registered users. That stat came just four months ago, which makes last night’s reveal quite significant and proves that Twitter is adding nearly 300,000 new users per day, as previously disclosed.

Of course, mobile plays a huge role in Twitter’s growth. Sixteen percent of new Twitter users now join via mobile device, as opposed to signing up on the web. The official Twitter mobile apps have significantly helped the company on this front.

This week’s Twitter for iPad unveiling could also help the company recruit even more new members through mobile. The application offers a fresh iPad-specific application experience with an innovative panel design.

BDST: 2015 HRS, 5 September 2010