A driver has a finite amount of brain power. When portions of that finite supply are channeled into a phone conversation, applying makeup, inserting a CD, daydreaming, unwrapping a candy bar, whatever - they are not all that focused on driving. Take a good look next time you are out on the road. An extremely high percentage of driver's are talking on a cell phone. As driver's these people are impaired - the majority of their focus is not channeled into their driving. Then you have the DUIs out there - alcohol, drugs, medication. There is an excellent chance that a driver won't see you due to impairment of one type or another. Heck, they crash into other SUVs - doesn't have to be something as small as a motorcycle. :shock:
It is probably a good idea to do what you can to improve your visibility. Headlight modulators, extra of flashing brake lights, additional side reflective material, reflective vests, riding with high beams on during the day - all that could help. But I wouldn't totally rely on any of it.
The most important thing is to ride like your are invisible. Assume that car next to you is going to change lanes and hit you. Don't hang out alongside a truck or car on the freeway if you can avoid it. Assume that the car stopped at a stop sign is going to pull out into your path. Cover your brakes and think out an avoidance route as you approach. Watch your mirrors when you are stopped at a light. Leave yourself an escape route if the car behind you doesn't stop and have your bike in gear - not in neutral. These tactics are way more important than anything you can wear or bolt onto your bike.