If you are not subscribed to these two comics, then this will be new to you. If you already have them on your RSS feed, well, you get to suffer their propagation.*
The ever-linkable XKCD offers the rational incentives on leaving reviews for hotels (and other places). Poor reviews may drive demand down, which should lower the price of your consumption.
SMBC, often delving into philosophy, science, and economics, has offered two economics-related comics in the past two days. Yesterday's comic posits the economists value of humans versus other objects and today's comic offers a, perhaps obvious, comic on the incentives of self-cat-napping (the bad kind).
*I'm directly linking to the comics so they will get the benefits of future readers, advertisment impressions, and the proper amount of web-traffic they deserve.