One of the great (maybe most under used?) Twitter features is mobile notifications. They are very valuable when used properly (ie following the right users) and overwhelming when used incorrectly (ie following too many people) - and Twitter recognizes this. Hence, Twitter is now recommending mobile notifications of recommended users on Twitter.com. Great in-the-river promotion that encourages cross device use (from web to mobile) and for users / content that they believe I will appreciate.