Part of this is that people who have never been online before don't understand the value of getting online. This allows them to have some access in order to better understand the value. The model is a bit like the old shareware model DOOM used - give a few levels for free and if they like it they can pay for the rest.
The backlash was the argument that Zuckerberg was only giving access to a few websites (mostly Facebook) in order to get more control of the internet without following net neutrality. To me this seems to be an oversimplified and overly pessimistic view of what happened.
The telecoms are not going to just give free access of the entire web to everyone, but by giving access to some valuable websites for free people may start to see the value and demand better infrastructure/start paying for mobile internet. I think Zuckerberg is being earnest here and not attempting to manipulate people for some malicious power grab - this seemed like a good approach (unfortunately the PR fallout was not).
In comparison it looks like google is just setting up free wifi hotspots which requires you to go to one in order to use it and is generally a lot less useful.