A trailer is another vehicle that must be maintained, insured and licensed.

I pull one with the bus most of the time. We have a 24' enclosed car trailer with GVW of 9900 and a open flat top single axle rig with a GVW of 5000.
The up side of the enclosed one is it is a little more secure and the trash the bus picks up beats on the trailer not it's contents, but it tracks well inside the drive and tag axles when turning and that can be a real buzz kill. The assembly is 73' and change and that can cause some problems all by itself.
As Jon indicated length laws in some states and parking for starters.

The other one we pull is much more user friendly the deck is 8'6" X 16' and we use it for ATV's, snowmobiles and such, the overall length with it is 65' on the nut and it tracks in the same path with the drives so if I don't hit it with the bus I won't hit it with the trailer. The downside to this one is your stuff is in the open.

One of the main reasons I like trailers is the fact that you can back the things up.

We are slowly moving toward using a frog for some trips and thats another vehicle, there is no end to this madness.