With the example of Harrison, it was more to avoid stacking academy players on top of each other, hence only allowing the bribe once per position. If he could get whatever he's paid now plus an extra £100,000 from the RFU to start at another premiership club it might overcome his loyalty. I did also bring up Simpson/Robson, which to me is far more damaging to England's development.
And on the club side of things, if somewhere like Gloucester could save/make money hiring Harrison (or keeping Robson) ahead of a naff Celt* like Laidlaw, it benefits just about all parties. See also: Jackson at Wasps, Hook at Gloucester, and Denton (soon) at Bath.
As was mentioned earlier, our ability to convert U20s to internationals is horrible. If someone can think of a way the RFU can stop 20-25 year-olds sitting behind cash-cows then we might actually improve that. Look at the development of Farrell and Ford when they both got regular starts at Sarries and Bath.
*Bit harsh, but I think they're limited players who are picked based on experience/reputation. If there's an English youngster with the potential to be better than them, then the RFU needs to intervene and get them starting. It's effectively trading our development for international rivals' player base.
EDIT: I accept there's some loyalty that won't be overcome, and always like one-club players, but there needs to be an incentive to spread out talent. Otherwise we'll see the top six hoard their academy products and spend five years filtering them into domestic rugby. Needs to be done far quicker.