The purpose of this article was to show that not all leakage patterns are easy to find. You may hardly notice some of them, may be due to the small bookkeeping objects that become obvious only after several thousands of iterations. Knowing the internals of a process is an undeniable key to success. Be aware of the leak patterns. Instead of debugging your application in a brute-force manner, look at your code fragments and check whether there is any piece that matches a leakage pattern in your arsenal.
Writing defensive code and taking care of all possible leakage issues is not an over-optimization. To take it simpler, leak-proofness is not a feature the developer may choose to implement or not depending on his mood. It is a requirement for creating a stable, consistent and forward-compatible code. Every web developer should know about it. No excuses, sorry. There are several solutions proposed for leakage issues between a JS closure and a DOM object. Here are a few of them:
However, you should be aware of the fact that there are always unique cases where you may need to craft a solution for yourself. That's it for now. Although the article is not intended to be the "best practices in avoiding memory leakage", I hope it has pointed out some of the interesting issues.