I'm not sure I would call it "free". Sure, you don't have to give google money, but on the other hand, you have to give them them all sorts of other info. This is not free. It's time people started acknowledging this.
While this may seem like semantics, it is the basis of communications, that we all agree on the definition of certain words, otherwise we have linguistic chaos.
So, yes, while it doesn't require any monetary payment (free), there are strings attached.
I know we think that paying makes us customers and they will care about us. However, it probably does not apply to naturally monopolistic markets of traditional/cell telephony and Internet services providers.
Additionally: "Google does not claim any ownership in any of the content that you or your callers upload, transmit or store in your Google Voice account. We will not use any of your content for any purpose except to provide you with the Service." http://www.google.com/intl/en/googlevoice/legal-notices.html
Come to think of it, does anyone know of where google makes money here? Is it just international calls? Even the voice transcription training probably isn't that lucrative, because you have to have users click on a message and say "Donate this voicemail" for it to be used as training data.
Who in their right mind would give something completely free, no strings attached?
Start acknowledging? I'm pretty sick of people mumbling "If you're not paying for a product, you're a product" every time Google, et al releases a free service.