More than three-quarters (76%) of online Canadians teens 12-17 now have profiles on social-network sites, and many of them on more than one site, DigitalHome.ca reports, citing Ipsos Reid numbers. That 76% is up from 50% in 2007 (eMarketer reports that 75% of American teens use social network sites). For Canadian adults, the number is 56%, up from 39% two years ago. Facebook’s No. 1 with Canadian teens, 93% of whom have profiles there. If anyone’s interest is lagging at any particular site, they may not be alone – see Lockergnome.com on the “lifecycle” of – I’m not sure – either a particular site or a single user’s interest in one.