Whether it's unethical, probably not, it's business. Is it annoying? Sh!t yeah!
The amount of times I've searched for names and variations only to see crappy holding pages everywhere is frustrating. Then going to Sedo and seeing some numbskull thinking he can get $5000 for a long domain name
www.word-word-word.com is almost funny.
It just inspires me to keep rethinking the name until I find one that I can get for the regular cost. There are still good names out there if you think hard enough and long enough.
There is one name I've kept checking for about 5 years, nothing has ever been added to it, the guy is just keeping it. The annoying thing is that I've emailed him a few times and I never get a response, so he isn't developing it or planning on selling it, so I don't know what his game is.
I'd like to see something like, when you renew after 2 years and a website has not been added then you cannot renew it. It's easy to place one page on a domain or even redirect it, but if someone can't even bother doing that, then I think they're being a pain in the ass. Holding up a good domain name can impact on a web business.
With land, local government can step in and force developers to develop or sell. With domains this can't happen - it's not exactly the same.