i am confused about this blackberry messenger over wifi thing.. it seems to work but i can not tell, i found this in a RIM publication
The BlackBerry® 8820 smartphone allows BlackBerry smartphone users with qualifying data
plans to access BlackBerry data services using a wireless network, a Wi-Fi® network, or both
All BlackBerry data services are available through Wi-Fi networks.
xxx8226; BlackBerry® Enterprise Server
xxx8226; BlackBerry® Mobile Data System (MDS)
xxx8226; BlackBerry® Internet Service
xxx8226; BlackBerry® Messenger
xxx8226; Personal identification number (PIN) messaging
xxx8226; Other data services xxx8211; instant messaging, etc
Having the option to simultaneously access both a wireless network and a Wi-Fi network
allows BlackBerry smartphone users to do multiple tasks at once. For example, a BlackBerry
8820 smartphone user can send email messages using a Wi-Fi network, while conducting a
phone call using the wireless network.
viewable at: http://na.blackberry.com/eng/ataglan..._Via_Wi-Fi.pdf
EDIT: my question was answered by the excellent chart on page 6 of this publication, shows what can and can not be done on Wi-Fi