While it is officially our responsibility to send contact requests, I feel like I send quite a few too many, and some pilot participation in keeping the airspace running as intended would be much appreciated.
Just my humble take on things.
Looking at the CoC, B3: A pilot must at all times check for appropriate air traffic control coverage for the airspace he is crossing at any given time. If there is an appropriate air traffic controller available
or upon request to make contact with an appropriate air traffic controller, then the pilot should immediately contact such controller.
It's not entirely our responsibility to send contact me's. The OR in the policy not only puts the responsibility on us but the pilots as well. I still think pilots, especially in Europe, have become so dependent on the contact me's that they come to expect it and if they don't receive one, it is entirely our fault.
This may be going into too much analysis of this policy, but it sounds like this was the initial intention for the policy, but then they had to add "or upon request" because no one was doing it on their own.
"A pilot must at all times check for appropriate air traffic control coverage for the airspace he/she is crossing at any given time. If there is an appropriate air traffic controller available, then the pilot should immediately contact such controller."
This is the way I look at it: I have found that the pilots who are on the network to be controlled, will contact you on their own. In fact, about 75% of pilots contact me without the use of that feature. The only time I would send Contact me's is when the aircraft will be going into an adjacent ARTCC.
If people get angry about it, I educate them on the CoC and ways they can find out where they are in respect to the controllers online (VAT-SPY, vataware ETC).
I have been doing this system for about a year, and I haven't had any major issues. That being said, I control in a ARTCC where there are not many overflights, so that may have an affect on the above points.