Microsoft subsidiary Skype hit 40 million concurrent users this week, the most users that have ever been signed on to the VoIP service at the same time, the company said.

The mark eclipses the 32 million users that were on the service simultaneously in February (not to mention the 34 million and 35 million user mark it anounced over the past several weeks).

Microsoft acquired Skype last year for $8.5 billion, causing some angst among users at the time worried that the deal would radically change how the company does business. And, to a degree, it has, it's raised awareness of Skype's features.

The company earlier this month launched a $12 million ad campaign in the United States and the United Kingdom aimed at highlighting the multiple features of the free VoIP offering. It focuses on "big, bold statements to grab people's attention and get them to think about how they communicate."

The campaign features billboards with messages like, "When did it become OK to text Mum happy birthday?" and "140 characters doesn't equal staying in touch." The company said it's focusing on the U.S. and U.K markets because the two markets are mature and important to Skype's growth.

A digital ad campaign also will debut April 19 on sites like CNN, BBC, Facebook, Lonely Planet, AOL, Yahoo, Wired, MSN, The Daily Mail, iVillage, CBS and Hulu.