Some people think Facebook, is a waste of time. And it may be - If you're inclined to waste time. You do not need to be if you learn to use it correctly.
There are plenty of less vocal people who believe StumbleUpon is for amateur sharers. And of course there is the big camp of people who think all social media, including blogging and social bookmarking, is a huge waste of your resources that you won't get anything back from. What's so often missed here is that, under different circumstances, the view of tools as useful and useless is right. A powerful weapon in the hands of a novice is ineffective.
Seriously though, it's always your choice whether to be a novice or to learn more. It's much savvier to say you don't know how to use Facebook for business, and then find out, than it is to claim it's a time waster when you're playing the Zombie game and bothering your co-workers.
The easiest way to overcome the lazy potential factor in any social media tool is to limit the amount of time you spend on it. If you have 15 minutes to get everything you need during a trip to the grocery store, the way you spend your time differs greatly. You'll bring a list; think ahead to how to most efficiently cruise the aisles, etc.
On the other hand, if you are taking a leisurely trip that's not needed, you tend to browse and look at things you normally wouldn't buy, not to mention spend too much. Plan your trips to social media sites the same way. You can always come back to play Scrabble or chat with friends, after you've finished your work.
I liken the use of Social Media to the use of the telephone (Yes, the internet too, but that's so obvious that the point is still missed. But heck, if you were smart enough to catch that, I guess you can skip to the end.)
You can use the telephone for dating (phone chat rooms), to waste time (gossiping with a friend), to solidify a relationship (calling a friend just to say hello), to touch base (let your mother know you're alive), and yes, for business too (call instead of driving over and having a meeting, connect with a client, check up on a vendor, ask a colleague a question, network, etc.).
It's up to you how you want to use Facebook, or del.icio.us, or MySpace or Furl or any Social Media tool. If other people think it's a waste of your time, let them. They are not the ones who have to live with your profits and losses at the end of the quarter. There's plenty of information about how to use Social Media Optimization for business, Facebook in particular. A lot of it is free.
If that's what you're interested in doing, don't let the "time waster"; scare throw you off - go out there and find out for your self what the best tips are and test them. Believe your own results, that is the rule of online search engine marketing