No, it wasn't. We routinely have the same conversations over and over here at HBT, and the answers to most simple questions are already here. The phrasing of your first post made it seem as if you were too lazy to use Google, a book, or any number of other means to answer your question. It's hard to help someone who isn't interested in helping himself (in this case, not you). Perhaps I was a bit harsh, and for that, I do apologize.
Ok, this is a much better jumping off point for discussion!
Once the yeast has taken hold and begins to reproduce and subsequently ferment, it tends to act as a natural "immune system" for the beer. The colony's activity tends to overwhelm any bacteria or wild yeast that come in contact with the beer. Then, as CO2 and alcohol are produced, the environment inside the fermenter becomes even less hospitable for infectious organisms, especially aerobic bacteria and mold. The combination of active yeast, CO2, alcohol, and hop compounds make beer rather resilient in fighting off foreign bodies.
Once the beer is completely fermented, it is far less susceptible to infection than when it existed as warm, sugary wort. There isn't much left for bacteria, wild yeast, and mold to "eat," and the alcohol content is relatively high compared to most substances found naturally, so an infection is even less likely than when fermentation was active. Assuming a relatively clean environment, the biggest threat to your beer when racking to secondary or to a keg is oxidation. A careful, clean, no-splash transfer will minimize the risk of both oxidation and infection.
After a keg or bottle is sealed, there is no way for an infection to take hold. If one was pre-existing, refrigeration will slow its progress, but there isn't much that can be done to stop it. Cool, stable temperatures will help preserve a beer's character, but there is no risk of additional infection after bottling or kegging.
So, indeed, in terms of infection, the riskiest part of brewing is during that time when the wort is warm (not hot), and fermentation activity has yet to begin.
& I'm going to bed now
), hot air is still rising out of the bucket/pot until its fairly cool. This should help keep airborne particles from falling into the wort since it has hot air rising off of it. This theory works for smaller vessels slightly better but I think the principle still applies. So from that stand point your only risk is stirring with a dirty spoon or drooling as you smell that amazing aroma. Another potential hot spot I would think is the hydrometer sampling. Though as long as you sanitize your thief or hydrometer you shouldn't get any contamination. There is the risk that airborne bacteria or fungi could get into the fermenting wort though promptness ensures that the exposure time is minimal. Also once things are fermenting along, the yeasts are the big fish of the pond. They've eaten a lot of the available resources and hopefully have made it hard for much competition.
