In an item on NPR's Morning Edition last Wednesday, someone who was talking about cul-de-sacs said this:
First, you can still hear the rumble of traffic on the nearby freeway. "And the other thing we hear are the birds," said Speck. "And that's actually the Scylla and Charybdis of the suburban condition. On the one hand, you do have this feeling of a close contact with nature, because you don't have cars going by every minute within the community. The only cars that come by are going to be the ones that are parking nearby."
On the other hand, there's the problem of having to drive your car almost everywhere. Or, in Speck's words, the uneasy feeling that "your car is no longer an instrument of freedom but a prosthetic device."
Mr Speck has used a wrong metaphor. Scylla and Charybdis do not represent the two sides of a situation, the good and the bad. In Greek mythology, Scylla and Charybdis are two sea monsters that live on either side of a narrow passage that boats must navigate. Veering too wide to avoid one put one at risk from the other, and successfully getting through the passage was difficult.
Thus, Scylla and Charybdis represent two equal difficulties or equally undesirable outcomes, both of one wishes to avoid, and to be between Scylla and Charybdis is to be between a rock and a hard place.