To me CallVantage and Vonage are "close" but aren't close enough to create confusion.
I know that some other VoIP providers (namely BroadVoice) have taken a lot of cues from Vonage in the way they design their web site; I'm surprised that Vonage isn't going after them too! Others, like VoicePulse, have steered quite clear of "looking like Vonage" and compete on their own merits, like features.
