I know wiser than I recommend keeping separate equipment, retiring old equipment when buying new in order to lessen the pain of owning two sets of equipment, but I'm totally fine with my cleaning and sanitation. Clean is clean, sanitary is sanitary ... two sets of equipment doesn't change that. I can see erring on the side of caution when offering advice, especially if somebody isn't quite there yet with those things (and we all like to think we are when maybe we aren't), but you've either got to be very unlucky (can happen to anybody and can't avoid it) or really do something messed up to infect beer.
I infected one batch once with something, I still don't know how. It was 10gal split 5gal in 2 FV's with different yeasts for each and one developed a pellicle. It wasn't a good pellicle either, I got a hoppy pale ale with a hint of baby vomit.