Funny (true) anecdote:
A few months ago I was at a stoplight behind a pickup truck with two young guys in it and two sportbikes in the back. I could see the bikes were secured with about 50 cargo straps going in all directions. The reason I remember this incident is because as I sat there, I had this weird premonition that something stupid was going to happen when they took off. So the light changed, and the truck pulled out to turn left. Sure enough, about mid turn I watched as a cargo strap or two flew loose, and both bikes dominoed over quite abruptly. One of the bike's mirrors went flying off to the side of the road. The truck quickly pulled off into a parking lot to the right, and I watched the bikes slide around banging into each other, and threaten to fall over in the other direction, with maybe a lucky strap or two on that side still holding them. Fortunately, no more parts flew out. I thought about pulling in behind them to see if I could help, then thought WTF, dumbasses.
I think most anyone towing a bike thinks their method of securing it works best for them. I do agree with fubar929, in that straps pulling both fore and aft are unnecessary. After a few popped seals and loosening tie down straps, I've long since quit using any of the gizmos that that attach to the handlebars, triples, or forks.
I do think that mechanisms that lock the wheels to the trailer bed work well, whether purchased, or in my case, angle iron rails I had made that solidly secure the wheels to the trailer floor. With my setup I've driven with no straps at all on bikes, and had no troubles. For longer trips, I use a cargo strap from either side of the bike frame to eyelets on the trailer sidewalls, but they really are just for my piece of mind. I've used this setup for quite a few years, and have surprised a few service techs when I can unload my bike in about a minute from start to finish. I know us tough long distance multi riders rarely trailer our bikes, but when we do, it's always best to have a solid, easy to use system, and not just wing it.
My 0.02