they throw it out because they don't want to hassle with trying to sell it at auction, or they don't want to try to put a price on it.
My dad picked up a LCD Projector (VGA/Composit/DVI/RCA) that we used to watch videos on. My dad ended up trading it for a 32" Sony Trinitron (which was $1k at the time) when we just stopped wanting to buy Lamps for the stupid thing. The nice thing is that we still have the TV, the bad thing is that we don't have the projector
He has gotten several nice things. He currently has a Pentium IV laptop that they were going to throw out when they ordered too many. Let's just say they ordered so many at the time, they had two extra for every person at the office. Since it was ordered through the company, they just told them to heave them in the dumpster. So instead the co-workers took them "under the table".
Other things have been docking stations for the laptops, Computer Monitors (my dad has a nice 17" LCD which was about 1 year old at the time) when from the last move they did.
My dad is so liked at the place that even after retiring, they call to tell him the latest batch of stuff they are throwing out.
I have a nice solid set of industrial wooden shelfs and full bookcases due to them deciding they wanted to repurpos the store room to a secondary conference room. So they were just going to throw out everything in it. My dad now has a 20' Ladder they used for getting on top of commercial buildings, he has those bookcases in the garage (we use it for out beetle and parts as well as tools), a SawZal, Creeper (under the car slider for when you work on them, no idea why that was back there), several bottles of NEW Freon for airconditioners, Table Saw, Router, and various other stuff like wire and copper tubing. It's amazing how full our house gets from this
They just don't want to deal with reselling and are in general are wastefull. They don't even try recycling it. I *almost* got a 20" ViewSonic monitor still in box, but it was pitched before I could get it. I later found out another coworker of my dad's scavenged it. Luckily it wasn't crushed by another person in the building (all they had to do was puch a button), so I feel a bit better.
It just sucks how wastefull companies are. I don't think it's people in houses that are so wasteful and putting polutants into the landfills, I think it's the corporations.
Anyways, I have gotten nice things from them like a few laptops (Like a Dell XPi, Dell CP) and various things like Ethernet-> Serial adapters that you can use to connect to a control panel or modem over the internet
The coolest thing about it is that I have the adapter hooked to a US Robotics modem (which i mentioned before there) and so I can connect through the modem and get on the net for free

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I used it a few times by having my mom put the modem on and I dialed up with a laptop from a client's house so I could get drivers. It was the FASTEST dialup I have ever used (the client had some weird ISP that required windows software to connect. The bastards...) so I had to use a dial in from a laptop to connect. Saved my but at that time. Going 4 miles on a bike was killer just getting there and back (2 miles each way) but doing that twice was something I wasn't going to do
It's so cool what you get if you get to them BEFORE they make you dumpster dive.