The NFL has long known that kickoff returns are among the most dangerous, if not THE most dangerous, play in the game. One attempt to address this came in 1975, when the league adopted a rule to prohibit a player on the receiving team from blocking below the waist on kickoffs, as well as on punts and field-goal attempts. Then in 2009, the use of a blocking wedge involving three or more players on kickoff returns was banned.
Of course, a well-executed return rates as one of the most exciting plays in the game and annually produces some of its longest plays, so to lessen the number of touchbacks, the league has actually moved the spot of kickoffs back twice. In 1974 it was moved from the 40-yard line to the 35-yard line, where it stayed for the next 20 years. In 1994, kickoffs were again moved, this time to the 30 yard-line.
This season, however, the spot was returned to the 35 in an effort to actually increase the number of touchbacks, lessening the runback plays that lead to so many injuries. NFL Commissioner Roger Goodell has gone so far as suggest kickoffs might be eliminated altogether in the future. A possible alternative he has mentioned is to give the team that would normally be kicking off after scoring possession of the ball on its own 30-yard line, but in a 4th -and-15 situation. A team could risk going for it, but more than likely would choose to punt, which is considered a less injury-riddled alternative to kickoffs.