[Superfly_FR]

The biggest increases in specific uses of data on the phone were seen in instant messaging services, with more than a fivefold increase in the proportion of BBM users in the past 18 months � from 3% to 17% of adult cellphone users living in cities and towns � and WhatsApp emerging from nowhere to claim a quarter of adult cellphone users.

Can't wait to have voice/vid activated on BBM
Data cuts into voice revenue with Mobile Internet use in South Africa

[DJ Reyes]

Seems to be the case in most places now. O2 UK recently released something that showed voice calls to be on the decline.