flashing rear in daytime important for safety
Distracted driving is the big cyclist killer in this day and age, people. Flashing lights, especially in daytime conditions, can make a big dang safety difference.
In the region around Kansas City, in about a 6-year period we had three separate accidents where very visible cyclists riding in daytime and excellent lighting conditions on flat wide roads with great visibility and no significant traffic were hit from behind and killed by drivers who HAD to have seen them from a long way away. We know that one driver admitted he was texting, one driver admitted he was entering an address in his car GPS device, and the third driver claimed he was arguing with a passenger in his car (bonus points - he hit and killed both a grandfather and granddaughter who were riding on the right side of an empty 4-lane road).
The real point here is that merely being very visible, without more, is not enough. Distracted drivers can see well enough to keep their cars on the road just fine without really "seeing" cyclists. A bright rear-facing strobe, though, will wake drivers up.
An earlier poster mentioned how flashing or changing lights grab our attention. We all know that - emergency vehicles, for just one obvious example, depend on flashing lights. But my favorite example about this is school buses: many across the country have white strobe lights on top. Stop and think about that. Something so huge and visible as a school bus needs a flashing light to help make it visible? The answer is yes, it's obviously very helpful for safety, and to wake drivers up.
I urge powerful rear-facing strobes for daytime riding, though there are lots of choices about the kind of flashing or interspersed flashing and solid that good taillights provide. I have given several good taillights to friends who are cyclists just because I think those lights really will help them be safer on the roads in this age of distracted drivers.