Writing an e-book is very popular among bloggers, as many have noted that “it's just a bunch of blog posts put together!” You will not only have to make an investment of time and energy to create the e-book, but market it correctly. However, if marketed correctly (through blogging affiliates in your niche, for example), you could have residual sales that last a very long time.
An obvious example is over exposure to bank stocks, which have been excellent investments for over a century. Though a foundation of most portfolios, bank stocks do involve more risk at certain stages of the economic cycle than many realise. Being less exposed to bank shares in the last few months could have preserved some capital. So, a more diversified approach can help mitigate some of these risks.