It does indeed "call home" in order to stay on top of current threats, but network connectivity by WV can be disabled either within the application itself or externally with a firewall. Personally I see much more downside in doing so (the bulk of my testing was done with the Network disconnected) as I have seen no evidence of WV identifying the user, looting data, packaging this data and sending it out to points unknown. But although the skeptical may say that say that absence of evidence is not evidence of absence (argumentum ad ignorantiam).
On the other hand, as I, nor anyone other than the WVSX staff, are coding the product, why believe that this or any application is safe to use and will always be (argumentum ad verecundiam)?