Communities are great. They provide support for many products and enable you to share the knowledge of others. Wonderfull!
The only drawback is that the communities of popular tools like PHP and MySQL consist mosty of enthausiasts and beginners. They mean well and they spend hours answering questions to the best of their ability, but they simply do not have enough experience to give the "correct" answer.
What's worse, as I mentioned in my other article "don't contradict the locals", forums are ruled by a few regular users who are considered to be the experts by the rest. They usually don't care about having the right answer, they care about being right and they will come up with the most idiotic reasonings why what their answer is right.
Consequently the bad knowledge is promoted and developers keep messing about with bad solutions.
PHP programers love the intval() function, and MySQL user's are quite happy to add a "GROUP BY" to every query, just in case...