The names are well known and they probably cost you handsomely in your MLB drafts, but it is almost August, and anyone remotely in the playoff race cannot afford to waste a single roster spot.
It is very hard to let go of the guy you pinned your hopes to in the preseason. You called out his name or clicked on his picture in the draft room and had a sub-3.00 ERA or 40 stolen bases dancing in your head when you did it. The time has come to let go.
NOTE: This list applies to a standard 10- to 12-team league. All of these players should be owned in deeper leagues, and you are right to have more patience with your stars in those formats, but in the vast majority of leagues, dump and don't look back.