Re: All that safety...
Again, I have to respectfully disagree.
relying on hearing in lieu of twisting your head around is bordering on gross stupidity. There's a reason they call it the 'lifesaver'.
If I make a move across a lane of traffic (small adjustments for road quality shouldn't count as, by rights, you really should be in the 'primary position' when riding), I value my life more than to ever rely on my hearing to inform me of any impending doom. Firstly, what if its a hybrid running on battery? (oh, the irony!) or another cyclist you are about to cut up?
Every turn, lane change, start, stop should be reinforced with a gander, and, where possible, eye contact with the following/relevant driver to assert your intention to do 'something'
Ill take your point on the cycle lanes though and, tellingly, probably wouldn't wear earphones on a cycle lane for just that reason. :)