It lead to the jailing of many innocent men, mostly academics, including Alexander Solzhenitsyn, who would write about his experience as a "Fifty Eighter" in his novels (chiefly The First Circle).
Sentences for the crime were long (5, 10 or more years) and frequently extended indefinitely without trial or consultation. If the prisoner was released, he would often be sent into exhile within Russia.
Section 10 of Article 58 made for somebody to be tried for "propoganda and agitation against the Soviet Union", whilst section 12 allowed for onlookers to be prosecuted for not reporting instances of section 10. In effect, Article 58 was carte blanche for the MGB to arrest and imprison who it liked, making for its use as a political weapon. People could be framed by the MGB - it would arrange an "anti-Soviet" incident in their presence and then try them for it. If they pleaded innocence, the fact they didn't report the instance would also make them worthy of imprisonment.
Article 58 was used by Stalin and his cohorts to imprison many returning WWII soliders on the grounds that their capture and detainment by the Axis forces during the war was proof that they didn't fight to the death and were therefore anti-Soviet.