Streaming a movie while you wait at the gate sure is convenient, but there are a few things to consider before you use airport WiFi -- not only when using your laptop but when using your smartphone or tablet, too. Airport WiFi is public WiFi, and public WiFi is unprotected. Don't send personal information while using public WiFi -- you risk losing your Facebook password or even banking information to a hacker. Always browse using a secure (SSL) connection, even when you're just checking your e-mail, and disable sharing.
Also remember to plan ahead. Some airports offer free WiFi and some will make you pay; some don't have WiFi at all.