I can understand a bit of cheating on an alt account, it's probably quite fun and an achievable way to see what other places are like besides your own. I don't get people who are playing the game like that and only like that though... then again I've never understood blatant cheating in any games. It seems even dumber in Pokemon Go where the whole point/fun is to get out of the house and relive some of the glory of the classic Pokemon games in the real world. It's like playing hide and seek without the seek.
There's a cheat app that has been around for over a month that is quite advanced and I'd be surprised if it even possible to detect people using it as cheating. It's not quite immediate GPS spoofing like teleporting (which should be easy for Niantic to pick up). You can pick a location that you want your avatar to go to and then you choose to walk, run, or drive there. Hatch eggs on the way like you would if you were doing it for real, all from the comfort of your couch. I have no idea how anyone could be caught cheating that way.
I guess if it weren't for Gyms it wouldn't really bother me. If the cheating becomes completely rampant (it's not so far in my experience) it'll be best to just to forget about gyms, fork up the $$$ for anything you want with coins, and focus on the Pokedex instead.
My mate started using this app today and he sent me a pic of a Golem he caught in town, probably forgetting the screenshot makes it obvious it's a cheat app lol, he's like "you can't teleport, you still have to walk", by that he meant the avatar still has to walk, he doesn't have to leave his house the little merkin.
I just hope this shit doesn't become the norm to the point it sucks all the enjoyment out of the game. /rant over