What I like about Vonage is they are always thinking ahead. So this idea, which I actually had and experimented with Webley back in 2002/2003 with using my Sony Vaio Picturebook, a hacked version of Windows Messenger and from Starbucks is really not breakthrough to me, but it is a great idea.
Make a WiFi phone that will work inside hotspots which require authentication to get on the network.
To accomplish this Vonage will need to get cooperation from the hot spot operators, and some type of advanced authentication will be needed. Perhaps what Bridgeport Networks is selling to the mobile operators.
What this means though is Vonage recognizes they have to work with partners and those partners have wireless access..Hello T-Mobile. Hello SBC...but the real hello could be Wayport, Boingo, i-Pass or GRIC all of whom have extensive networks already WiFI ready and VoIP capable.