The big issue with charges like this is clarity of cost. I imagine that despite there being a no cost option, most passengers will actually pay the extra to choose their seat. As this type of "extra" charge increases, it becomes harder and harder to compare prices and to realise what you are actually payung, but keeping "headline" prices down.
I don't fly RyanAir, so I may be wrong, but a friend who flies with them often, told me that with them you have to pay to check in - however you do it. There is a smallish charge to check in on-line, or a bigger charge if you do so at the airport. When it gets like that, it is just silly, as there is no zero cost default option.
BA are usually my preferred choice, but despite my jokes in the post above, it is important for my family and me to be together, I feel that I am almost forced to pay the extra charges with BA to ensure that (as others have said, you can't shift other pax around to accomodate a group if the others have paid for their specific seat). My gut feeling is that BA will no longer be my preferred carrier as the cost will be so much more.