Andy Abramson has a post that Vonage has backed out of VON Canada because its PR firm doesn't believe there is enough of a consumer play. This would be a big blow to the show given Vonage was likely a major sponsor of the show, which was plagued last year by an overly-large venue and a lack of "star" keynotes. Andy suggests Vonage's decision suggests it is not doing well in Canada - a claim that seems plausible given you hear much more about VoIP service from the big cablecos, Rogers, Videotron and Shaw. A quick check of the exhibitor list for VON Canada does not include Vonage.
Update: Andy has another post on speculation Vonage is closing to filing its S-1 with SEC as part of its IPO plans. He speculates maybe that's why Vonage isn't going to VON Canada given there will likely be a blackout period to do pre-IPO marketing.