My bad habits include: using municipal tap water without boiling to top up a boiled wort, rinsing bottles with hot tap water prior to bottling (no other sanitizer), rinsing a dishwasher-washed spoon with hot tap water and using it to fish out some yeast cake for a starter, using the same buckets/siphons to brew sour beers and regular beers.
I'm of the opinion that when you clean a surface completely, theres no food for a bacterium/yeast to use to stay alive. Therefore I thoroughly clean bottles/buckets/carboys right after use, and then rinse them before the next use to remove any dry particles that floated in.
Thats along the lines of my comfort level. I'm not advocating it for anyone else, but I do periodically tell people just so they its not a slam dunk that you'll get an infection if you don't use conventional wisdom in sanitation. You're simply going from a relatively low probability event, to an even lower one.
The one other observation I'd make is that the key to avoiding a serious infection is to have vigorous yeast and plenty of them. Theres always competition with wild bugs if you aren't working in a sterile environment, so having an army of yeast to outcompete the occasional wild critter is key. It always happens, and is why the yeast manufacturers recommend getting fresh yeast after four or five generations. I think I even read that in White's Yeast book.