In the season of it's introduction, Adrian Sutil was the first to discover the propensity for unexpected spin when he deployed his DRS early exiting a corner onto a main straight. I can't recall the circuit although I do remember it was in free practice. That the straight was quite wide, and that no-one was directly behind him, was pure luck, otherwise it had the potential to be a very nasty accident. It was following that incident and a couple of similar scares that rules were tightened and activation zones set further away from corner exits.
Interestingly that was never going to be an issue with the so called F-Duct since the drag reduction conferred by that was less dramatic and had a more incremental effect in relation to the speed of the car. That's just one reason why, IHMO, that should not have been banned only to be replaced with the DRS whose use is not entirely under the control of the driver. I also think that if a device is on the car it should be up to the driver as to when and how to use it.
IMHO, F1 has never really been about being "fair" and it's not supposed to be a Mickey Mouse spec' formula for amateurs. Imposition of the DRS is just another symptom of a failure to allow designers and engineers the latitude to explore innovations in every aspect of the car designs. The result is that ever more money is spent to refine elements within ludicrously constricting regulations and the team that finds the magic bullet at the start of a season will likely as not streak off into the distance. That there is so little room for development within the reg's was one reason Red Bull dominated four seasons and Mercedes is likely to dominate this one and possibly more.
It seems that the sport hasn't learned anything from the past fifteen years and, surprise, surprise, this week we have another raft of daft ideas to spice up the show circulating in the rumour mill
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So, how to make the DRS fair ... either ban the fucking thing or de-restrict its use. If it leads to drivers messing up then that's part of the sport. After all the cock pits are such effective safety cells the odd smash will add a lot of the spice people are looking for.