Normally the EUR and CHF show similar risk profiles and are mostly measured against the USD, with very strong inverse correlation. That's why the EURCHF mostly flat-lines: they move more or less in sync.
Recently, however, the EUR has been battered by the crisis in Greece and next possibly Spain, so the balance to the CHF was disturbed and EURCHF started moving down. To the level that the SNB is rumored to consider their intervention threshold. Like a self-fulfulling prophecy, the pair spiralled out of whack. Whether there was actual intervention or not, I don't know.
What's the take-away? Only sell the CHF, especially when break-outs happen (i.e. buy USDCHF, EURCHF); not many trading opportunities, but market psychology is on your side.
Spikes after interventions tend to retrace violently, so it's a good idea to lock in profits fast.
jesper