In England, Crown agents originally controlled bail. As the executive branch of every Government surely will, this power was abused. When Parliament stepped in with laws, the King's judges deemed the accused might be held without bail upon the Sovereign's command. This went back and forth for decades in the 1600’s, as laws were enacted and despots found loopholes. Eventually, when judges were compelled to set bail, they jacked up the amounts of bail to accomplish their objective. Finally, the English Bill of Rights (1689) held that "excessive bail ought not to be required."
Fully cognizant of this history, James Madison demanded our Constitution state "bail shall not be required," rather than "bail ought not to be required." The legitimate use of bail is on a case-by-case basis. It must provide a reasonable guarantee that the accused will show up for his trial. Character and previous behavior of the defendant must be considered.

When you have no right to liberty pending trial by payment of bail, it is much easier for Government to prepare its prosecution than it is for you to prepare your defense. When the relative danger you pose to the public has no bearing or whether or not you get bail, Government can hold you and free others arbitrarily. When judges can levy harsh bails on enemies of the state, the pressure by Government for them to do so will mount.
Despite the term "excessive" being itself arbitrary, the Eight Amendment would require multiple levels of the judiciary to become entirely corrupt before prosecution becomes persecution. Watch out for news of extraordinary amounts of bail being set for nonviolent “national security” offenses – this may be a sign that the kind of tyranny that plagued England 400 years ago is underway in this country.