Sometime near the end of February, estimated to be February 25th, Twitter is going to get account number 500 million. Currently the service is adding 11 accounts every second. This in part is a result of the deep iOS integration unveiled last year.
This is turning out to be the highest staked catch-up game ever as Twitter trails and plays catch up to Facebook and others. Facebook is a few months away from hitting the billion user mark, while China-based Twitter clones, Sina Weibo and Tencent Weibo passed a combined 550 million users late last year.
Regrading Twitter, it is also worth bearing in mind how many of those accounts are actually alive and active and how many are spammers. Spam is an issue that continues to plauge and harass Twitter users on regular basis. In September, Twitter announced that the number of active Twitter users per month stood at 100 million, while Twitter.com received more than 400 million monthly unique visitors.