The airlines are hurting. Everyone is in this economy, but it's particularly evident in the airline industry. I took a round trip United flight, and I was simply stunned by the sheer amount of upsell they try to do during check-in.All checked bags are an additional fee now: $15 for the first, $25 for the second. And you have the option of upgrading to Economy Plus (i.e. the amount of leg room that all of our seats once had), and they even try to sell you more frequent flyer miles.
I was a bit peeved about the luggage fee. But the since flight was free (using up my frequent flyer miles, before United goes under for good), I suppose I got a pretty good deal overall. And on the trip, I did figure out how to check your bags for free. I plan on doing this in the future. I encourage you and your friends to do the same.
Since all airlines are now charging for all checked luggage, most people now bring "carry-ons"--and I use that word quite loosely. The vast majority of these bags are rolled, dragged or lugged on, but never carried. With so many travellers carrying on, the overhead bins are full before the plan is even halfway boarded. So now the rest of the passengers are getting on with their luggage, and there's no where to put it. Well, there is the space under the seat in front of them, but let's be honest; it would simply be too base, too inconvinient, to stow it there. As if that monstrosity would even fit.
These poor souls are now wandering up and down the aisle staring wide-eyed at the row of full bins. They absentmindedly open the closed bins, as if one of these will magically turn out to be empty. It never is.
At this point the flight attendants are doing everything they can to get the plane boarded and pushed back for an on-time departure. They're not going to charge you to check that bag. They don't have time to deal with processing credit cards and making change for a $50. They happily take your bag, slap a tag on it, then fling it out the door for the ground crew to deal with.
So that's the secret: Carry everything on, then check it at the gate. It's more limiting in that you have to abide by the TSA rules du jour, but hey, you'll save enough for a nice meal at one of the fine dining establishments at the airport.

Word has it they're going to start enforcing carry on size limits and put the templates over the x-ray machines to screen out bags that don't fit.
Fun!
I don't think that will work more often than it won't. The airlines will work out the incentives such that the attendants will be more interested in happily annoucing that takeoff is delayed because of Mr. John Doe's stupid luggage that he should have known would never fit in an overhead compartment, while pocketing a $2 bonus for increasing airline revenue.
As an alternative, how about booking all of your flights with a connection in Toronto? I think that most airlines still allow two free checked bags on international flights.
That's why I called it a game. This is the latest move we consumers can make. Enjoy it while it lasts. After the next move by the airlines, we'll have to figure something else out.
Joe, I don't see that happening since 20+ passengers will be in the same boat. They're not going to humiliate all of them, and in fact it'd be bad business to publicly humiliate any of them. As bad as airlines already treat passengers, I doubt they are stupid enough to cross that line.
"the same boat"? I thought we were talking about planes? J
It's been nearly four years since I've been on a US domestic flight, but I don't recall seeing 20+ passengers trying to move carry-on baggage to check on. That certainly may have changed as the new baggage charges are implemented and more people start playing your game...but while the overt public humiliation may not take place, I definitely see them starting to stand their ground and demand payment for any obvious carry-on infractions. Or perhaps there will be more stringent checks at the gate. Anyhow, the airlines have already shown that they are willing to squeeze blood from a stone(*) to try and get their operating margins down, so I'm sure that they will ultimately do the same to increase revenue as well.
(*) http://www.nytimes.com/2008/06/11/business/11air.html
I like this comment from the above article: "Remove the overhead bins. This will force passengers to carry only what will fit under the seat, eliminating the weight of the bins."