Coming back to DEN on Tuesday night from ORD (and points much further east), I noticed at the DEN baggage claim some bags from the LATER flight from Chicago.

Additionally, I was told by some folks that some bags from our flight made the EARLIER flight and were lined up on the floor and waiting for them.

How did I notice this? I don't normally, but I saw several bags with UA 259 tags when my flight's bags were coming out. I only noticed the discrepancy the next day, because there was a story in the news here about two people being questioned after having a confrontation with a flight attendant (it sounds like it was a verbal confrontation about a kid walking to use the lavatory while on the ORD tarmac). My flight touched down around 7:15pm, 259 landed around 8:30pm.

The question here....has bag matching gone by the wayside?

The rule before was that there either had to be bag matching or bag x-raying. Now that all baggage is supposed to be x-rayed, bag matching isn't required.

Bag matching means that there are people that belong to each bag and those people are on a flight. As long as the numbers match, it doesnt matter that some luggage is split off to another flight.

Then why do baggage handlers sit with those portable scanning devices at the base of the ramp when loading bags onto planes?

But if the scenario is as you describe, then someone is lying. I have been told by dozens of airline staff over the past three that I cannot deviate from my itinerary in which I have checked a bag.

Then what would happen if a person checks in early for his flight, the bag makes an earlier flight and then the person decides not to board his flight (besides that his baggage ends up where he is not )?

It seems that this would also be inconsistent with the purpose of bag matching since a person checks a bag and then after it is on a flight, he decides not to fly.

Consistency?!? HaHa, that's a good one! I think that the whole airline universe is intentionally inconsistent to keep passengers and terrorists from becoming too comfortable with routines. Between fare rules, cancellations of flights, luggage, and of course TSA procedures, practically impossible to predict what will happen. End result, we are all safer, but less certain...

Airlines ought to let you stand by for an earlier flight even if you've already checked bags under these rules. I know either to let them know at check-in that I want to stand by (and thus get the bag specially tagged) or else not to check bags at all... but one of the reasons they claim to not let you stand by for earlier (or later) flights if you've got checked bags is "security," which is complete and utter BS the way it really works out.

Big hole isnt there?

Some misconceptions about PBM here. The rules (which may not always be followed, human nature being what it is) is that the passenger and checked bags must travel together on the first or only segment of the itinerary. How the airline decides to treat the bags on subsequent segments is up to them. Several times on short-headway routes bags may arrive before the passenger, having made a ramp cnx sooner than the passenger could in the terminal. And sometimes the bags don't make the same cnx and arrive later, sometimes much later . How do you think 'lost' bags get reunited with the passenger ? They fly unaccompanied (gasp !) and this is not perceived as much of a security hole if any, because of the very unpredictable nature of it.

If a passenger does not show for the first segment, the bags will be offloaded. I'm sure I'm not the only one who has been delayed on a flight due to this.

hth