Obi, I dont mean any disrespect, but I dont think thats fair. I'm not saying it's illegal to see the other persons team before they use it against you. But to be fair, they should look at your team before hand aswell.
Yet no one is going to say, "Hey, I saw your trick room team, so heres my anti-TR team, so you can switch if you want." Basically, they lose what would otherwise be the element of surprize. Which could be a huge factor on some more gimmicky teams. Now I know people will figure out rather fast what you're running based on what your kickers are. But if they were running an unconventional move. A lame eg. is leaf blade/close combat on gallade. You would think twice before bringing on your slowbro.
 
But on the other hand, Nintendo certainly didn't directly say that you can't look at other peoples teams. Nor did they put you in any situation where it would be hard/unlikely to see them (I heard some where even broadcast on the TV). Yet I'm sure the reason they did that was to show off pokemon not just to give certain players the edge.
 
So I guess where I stand is; I, personally, would never look at another persons team before hand. But like you said Obi a good player uses everything to his/her advantage. So it would seem to me like the best option would be to creep on other players as often as possible. For his/her game playing style more than anything else, because they to can switch up the team. But also carry several other teams, and switch off between them, while having a unique playing style for each. So that you don't become predictable yourself.