Although the U.S. Constitution set up the most successful republican government to date with a generally incredible respect for individual liberties, it is not without its faults. Yes, the American people improved upon (and sometimes detracted from) the original document as time went on, but one of the continual flaws in the Constitution existed at its inception: eminent domain.
At the time, governments routinely commandeered property from private citizens for any purpose they desired. The Founding Fathers, aware of that tradition, decided to limit it by requiring in the 5th Amendment that all takings relate to one of the enumerated duties of Congress (i.e. "for public use") and that the owners be given "just compensation." This does not make any taking moral since it is still done forcefully, but it was a step forward in human progress.
Unfortunately, in 1954, the Supreme Court took us two steps back by unanimously ruling in Berman v. Parker that the government could arbitrarily take unblighted property ("unblighted" because it had already been taking blighted property without justification) so long as it possessed some "public purpose" -- in this case, making Washington, D.C. "beautiful as well as sanitary."