For the past month I have been examining the effect of WiFi off-loading based upon my usage habits. To do this leave WiFi turned off so my phone only receives data service from a commercial carrier network. This was not a simple task because the Smartphone network optimizer will continue to request to have WiFi turned on and whenever you are using location services (Google+) not having WiFi provides a notification "to improve you location, please turn on WiFi".
My typical monthly data usage averages around 1.3 GB per month with WiFi enabled. I travel infrequently and have WiFi both at home and work. I think it is important to note that my work WiFi doesn't block YouTube, Pandora, Facebook, or WatchESPN, but I typically use a WiFi only tablet for music streaming or the watching a major sporting event e.g The America's Cup or the MBL playoffs.
In the month of September, I ran 5.7 GB of data in what I consider to be a typical work month. What this equates to is 3.4 GB of data that was off-loaded from the carrier network to the WiFi network for which I also pay. Another way to look at it is that my carrier only sees 1/3 of my usage.
Using some of the wholesale data rates that have been thrown around in the trade press, $5/GB; the cost to support my data usage through a WiFi Off-loading provider would be $17/month. If I am paying my carrier $30/month for my data usage and they pay a Wi-Fi off-loading provider $17/month, they only end up with $13/month to offset their operational expenses (site leases, backhaul costs, employees...)
When you consider the "true" smartphone usage and where the majority of that traffic is handled today, it is clear why cellular carriers have been reluctant to purchase wholesale access to data or a WiFi off-loading partner.
Check back next month. After my billing period closed, I spent the weekend out of town, so streaming two college football games on Saturday (Dish Anywhere) and 1 NFL game on Sunday will all be part of my October usage. With just 9 days on my billing cycle, I have already consumed 3.3 GB.