Actually, under US Copyright Law, buildings constructed or that had plans or drawings completed by December 1, 1990 can be copyrighted as an architectural work (see section 102 of the Copyright Act, 17 USC). This does not include buildings, such as bridges, cloverleafs, dams, walkways, tents, recreational vehicles, mobile homes, and boats, however; those could possibly be protected under trademark.

Taking the time to find this information is easy. It's all right there at http://www.copyright.gov/. Any artist who plans on publishing work (including in the internet) needs to understand copyright and what he/she can or cannot do. You (collective you not specific to anyone) certainly would want to protect your own work and should be just as concerned about honoring the protections of others.

Edited to add:

Disagreeing with a law does not give you the right to ignore it. When it comes to using anothers copyrighted work, you have an obligation to understand copyright law and respect copyright protection whether you like it or not. If you don't and you get caught by the copyright holder you may end up in the poorhouse and at the very least you will end up disrespected and with a bad reputation.

It's all fun and games...
Until the flying monkeys attack!!!