There are essentially two types of stare decisis. One is the obligation that trial courts have to honor the precedents of higher courts. A local trial court in Mississippi cannot legally convict a person for flag desecration, for example, because a higher court--the U.S. Supreme Court--ruled in Texas v. Johnson (1989) that flag desecration is a form of constitutionally protected speech.
The other concept of stare decisis is the obligation of the U.S. Supreme Court to honor past precedents. When chief justice appointee John Roberts was questioned before the U.S. Senate, for example, it was widely believed that he does not accept the concept of an implicit constitutional right to privacy, upon which the Court's decision in Roe v. Wade (1973) legalizing abortion was based. But he implied that he would uphold Roe despite any personal reservations due to his commitment to stare decisis.
Justices have different levels of commitment to stare decisis. Justice Clarence Thomas, a conservative jurist who often sides with Chief Justice Roberts, does not believe that the Supreme Court is bound by stare decisis at all.
While stare decisis is a helpful concept vis-a-vis the preservation of rulings that protect civil liberties, excessive commitment to stare decisis would have prevented such rulings from being handed down in the first place. We hope that conservative justices support precedents set by the anti-segregation ruling Brown v. Board of Education (1954) on the basis of stare decisis, for example, but if the justices who handed down Brown had felt similarly about the "separate but equal" pro-segregation precedent set in Plessy v. Ferguson (1896), stare decisis would have prevented Brown from being handed down at all.