Facebook is an extension, not a tool (it could be a tool but people usually don’t use it that way). A tool is an instrument we use to make things. An extension is how we project ourselves into things that surround us (cars, television, phones, gadgets and so forth.)
As an extension people just get lost in it. Facebook makes you wasting your time. 99% of the content on Facebook is useless and if you’re looking for something useful you’ve got to go through that 99% of garbage, that makes you wasting even more time. If you’re not looking for any interesting stuff, then you’re wasting your time in the first place.