6 Gym Slots? Really. Sigh

Although they mentioned nothing about it, I hope defender AI will be harder to beat now. That could compensate.

Now spoofers really won't have to worry about those pesky casual players sticking something in a gym...

I assume you're making the assumption that the fact collect system will be similar in that we collect up to 10 Jim's a day? Perhaps this won't be the case, perhaps there will be something new in its place or perhaps Niantic will implement a limit on the number of Jim's a trainer can actively have Pokémon. I would assume that they have kept this in mind when reducing the number of available slots, as they are aware that Jim placement is already an issue with spoofing. Let's hope for the best and see how this turns out, I hear your concern though.

I am using Siri and I noticed that she spelled GYM as Jim

I'm concerned about this as well. Unless they add new gyms, there will be 40% fewer spots to go around. Hopefully they add a hard max per trainer (15?) to help account for this.

I used to hold anywhere from 25-30 gyms. It is what I find fun and enjoyable in pokemon go - gym battling and prestiging. Having said that with only 6 gym slots and the possibility of spoofing going rampart - being able to drop an unlimited number of mons in gyms without needing to prestige - it could really get out of control.

I'd be very supportive of limiting gyms to 15-20 max or something like that. Anything to help combat spoofing. I would spend a lot of time prestiging up our gyms to open spots for other trainers but with only 6 slots this is going to be tight, very tight.

That and no more prestiging. Hopefully I'm wrong but that's a whole lot less different useful pokémon to own, bye bye diversity. The other changes look promising though.

If the rewards for attacking a gym match those for being in a gym, then it might not matter much how many slots are available in gyms. Also, you get rewards for feeding berries to Pokemon in a gym even if they belong to a fellow team member and not you. If you can get such rewards even if you are not in the gym, that would alleviate the problem as well.