Penny is a freeloader

In "The Big Bang Theory," (tv show) Penny, an aspiring actress who supports herself by waitressing, takes advantage of the kindness and resources of her neighbors, Leonard and Sheldon. Leonard and Sheldon are roommates who also work at the same university. Both, Leonard in particular, are benevolent to Penny, so she enjoys free Wi-Fi, meals, or help with various tasks. In this case, Penny benefits from the goodwill of her neighbors, without having to pay them back.

Now, this pattern of behavior mirrors the classic case of the "free-rider problem". The free-rider problem arises when there is a reluctance to contribute to the cost of goods that bestow group benefits. If a public good or service is being provided, some might benefit without contributing to its production. In this context, we can highlight the Wi-Fi conundrum. Now, I know what you're probably thinking: "Wi-Fi is excludable, so this example is rendered moot!" And yes, you would typically be correct. HOWEVER, you see, we haven't considered Leonard's kindness toward Penny, rendering him incapable from excluding her usage of Wi-Fi. And hence, we have the free-rider problem.