I'm going to give a breakdown on WHY SwagPlay is being suspected because some people just don't seem to get it. I'll attempt to address the common arguments against banning that I've seen both in this thread and on the Facebook discussion.
So why are SwagPlay or Prankster Swag bans being considered to be on the chopping block?
Prankster + Swagger creates immediate danger for your opponent, if not also for the user if they can't hit you with physical attacks anyway. Even something like Rotom-W still has to hope that it hits you while you continue swaggering it. Sure, it won't eat itself up immediately like physically oriented attackers but your Prankster still has an opportunity to sub up while Rotom switches or hits itself. It creates a very low-probability coin flip situation that makes it incredibly hard for your opponent to consistently hit you. Now, if they DO break through the confusion and somehow manage to sweep your whole team (probably not going to happen with the next prankster coming in), they beat almost unbeatable odds. In either situation, skill is completely irrelevant.
Common arguments for keeping Prankster SwagPlay
1. Confusion is an inherent mechanic of the game.
This was mainly on Facebook and is a horrendous argument. Smogon is not looking to change game mechanics! The Sleep Clause mod is a one-time exception to this rule.
2. If we ban SwagPlay, then we'll end up banning hax and what's next, Light Ball Pikachu?
Another common Facebook variant. These are slippery slope fallacies and have no place in a serious debate environment. Glad we have those two out of the way!
3. Magic Bounce exists.
This is where things get subjective but the selection of Magic Bounce users is rather slim. Espeon is a cool niche mon but is not really suited to handle a team with Foul Play. Sure, it's not THAT strong but it's pretty easy to chip away at it. I've seen others in the thread say that Foul Play does around 25% and I'll take their word for it. Xatu has an even smaller niche than Espeon and is only used for Magic Bounce. Absol has to M-Evolve first so it can't switch in on Swagger.
4. Lum Berry exists.
It works one time so you can't even switch in without getting re-swagged. Not much else to say about this.
5. Just use Blissey and stall out Prankster. Just include (niche Pokemon / move that you would never ever use).
Yeah that's a lot of fun. Just waste 200+ turns stalling out entire movesets of ~4 Pokemon. Let's not encourage hour long ladder matches please!! Also, no one wants to build a team around countering swagplay. It restricts your team building for something that you're not always encountering on the ladder.
6. It's just as luck-based for your opponent as it is for you.
This is actually not helping your case because you are admitting that the entire match is based around luck. Which is not a far cry from the truth! This complete reliance on luck totally undermines the concept of skill.
7. Yeah but Focus Blast / Rough Play / Sleep Powder / Leech Seed / Toxic / Will-o / Stone Edge / Fire Blast / Hydro Pump can miss and cause bad luck situations also.
Except both players understand those risks going into a match. Terrakion loves that STAB Stone Edge and Rotom-W adores Hydro Pump for coverage. Rotom-W enjoys crippling physical attackers with Will-o. Focus Blast makes Tyranitar wary of switching in on Gengar / (insert Psychic-type here). Those moves can miss and the opponent gets to sigh in relieve but when they hit, they can be devastating.
I know I can expand on these arguments but I'm trying to keep this as short as possible. What I want you to take away from this, though, is that SwagPlay creates a lucky / unlucky situation for both players. It's incredibly easy and cheap for the user (hence less skill), and frustrating and nigh uncounterable without niche counters, making your opponent's skill become irrelevant. Less skill vs. no room for skill.