You've heard it all before, in tons of brainstorming sessions. And truth be told, most of the ideas you hear *are* bad. But that doesn't follow that they're wasted. I've read some articles lately on the wasted time of brainstorming--"come with a plan, don't waste people's time" is generally the tone. And of course, no one wants their time wasted.
But true brainstorming sessions are rarely a waste. If done properly, and if people do some homework first and know the goals or objectives of the session, they can be a huge reservoir of ideas for the future--aside from finding a great nugget of an idea to use now.
The key is in the prep. If you barge into my office and ask me for 3 campaign ideas, there's a fantastic chance that all 3 will be a joke. But give me a day to come up with 3 good ideas, there's a good chance that at least one of them can be a jumping off point to something we can use.
So give brainstorming a chance--in fact, schedule it in when you're kicking off a project. You never know who's been holding back an awesome idea and is just waiting for the right time to spring it on the team.