I'm personally very against the idea of certification for fell running as in diving - it was a large part of the reason I gave up diving years ago to concentrate more on running (that and the small return in time actually spent in the water compared to the expense, hassle and bureaucracy of getting there, I realise its different nowadays with drysuits and rebreathers etc, which has been nearly enough to tempt me back. Its more complicated but the returns are greater, justifying the need (Malin Head wrecks? Port Napier was regarded as a serious dive in the 1970s!).
I would like to think that fell running operates in a similar way to climbing, ie you go out with a more experienced mate who (literally) shows you the ropes, you build experience, you begin leading, you move up the grades but nobody asks you for a log book or qualifications unless you are instructing other people for money. And many people come in to fell running from a mountain background and already have a lot of the skills and knowledge needed to operate safely in that environment. Perhaps this is what has changed - runners taking to the fells instead of walkers/climbers extending their activities to running?