of course desktops and laptops have mikes.
what do you think Skype does?
read your lips??
Read my lips (or just the text you replied to), I said desktops. Most laptops (and "all-in-one" computers) do have microphones and cameras, but desktops typically require you to buy a microphone and plug it into your computer. Try loading skype onto your desktop without plugging in a camera and microphone... The camera and mic in laptops can usually be easily disabled. Regardless, facebook can't take control or listen in without you loading software that allows them to do so.