[leoedin]

Google gathered wifi data to improve their location services. The capturing of unencrypted payload data was an unintended consequence of that due to poor software design. The initial wifi data collection was intentional and was designed to improve their location product (which it did - the Google Maps location service can be very speedy if it's near a wifi access point that google cars picked up - another feature likely to encourage people to use their product). The additional capture of packet data was unintentional. Numerous third parties have been involved in auditing google in their actions after it all came out and there's been no hint that they ever intended to do anything with the packet data they collected.

Facebook (and google) do "harvest" your data. They also mine it for relevent information from which they can show you adverts. There's no debate about that. It's not a conspiracy though - they state in their privacy policies that they'll use your data for targeted adverts. It's their revenue model!