Adam, be aware your question makes it sound like you're wanting to rape someone else's data store without paying for it. Contacting the WiGLE admins would be the correct way to go if your intent is on the up and up.
Not really. It's just another potential use of the information that the WiGLE project provides. Are you saying that people who are using WiGLE to find free wireless APs are also "raping someone else's data store without paying for it"?
GPS locations associated with MAC addresses only show an approximation of location. Depending on how many times the network has been seen and what equipment was used and the QOS rating, the location could be miles away from the actual AP. The GPS location recorded is the location of the device recording it at that point in time, not the actual AP. I could have an amplifier (I use one) with a cantena (or multiple antennas, I do) on a hill and record many AP's from a long distance that would all show as being where I was sitting when I recorded them, not where they were actually located. If you drove a circle around "each" network out there, then you'd have a "better" location, but due to the nature of how the 2.4 GHz wavelength signal is so easily scattered, it would still not be correct. I could go on and on, but perhaps you get the idea.
I agree - GPS locations associated with MAC addresses do only show an approximation. For some applications of location-awareness, all you need is an approximation. For example, using the data in the WiGLE db, I could build a weather app that shows a user her local weather forecast without initially asking her to input her location (but giving her the option to correct/switch locations). That's a simple example - there are tons of other applications that approximated GPS locations could empower.
That said, you could improve approximations for APs that have been seen multiple times at multiple sets of GPS coordinates (the simplest way to gain a major improvement would be to take the midpoint).