There are some tracks that somehow always seem to manage to produce drama. Sometimes, drama which affects the trajectory of a championship. Barcelona would appear to be one of those tracks.
Take 2006, for example. Loris Capirossi came into the Barcelona leading the MotoGP championship, tied for points with Nicky Hayden. At the start, his Ducati teammate Sete Gibernau took a line crossing from left to right in an attempt to gain places. Gibernau clipped the rear of Capirossi's bike, jamming on his front brake and causing it to cartwheel end over end through the pack. Capirossi was forced into Marco Melandri to his right, the pair of them going down and resulting in a massive pile up and forcing a race restart.
There were a couple of consequences from that crash. Capirossi escaped injury, but was battered and bruised. Unable to take part in the race, the Italian lost 20 points to Nicky Hayden, and limped through the next couple of races, effectively ending his championship challenge. And it was the incident which started the discussion about making brake lever protectors mandatory, though it would take until 2011 to get the rules pushed through in all three grand prix classes.