So Skarner is now made to give free vision to the enemy team?

"Skarner’s presence causes crystals to spawn in set locations around the map. Crystals can be captured by either team by standing on top of them. Capturing prevents them from being captured by the opposing team for 10 seconds."

"Crystals remain captured permanently for the capturing team until recaptured by the opposing team Capturing a crystal grants 15g to players that helped capture it Crystals are locked out of being recaptured for 10 seconds after being captured While on the 10 second lockout, crystals provide vision in a medium area around them (and provide no other vision the rest of the time)"

So, no, they don't provide vision permanently, but they do provide gold to the opposing team.