User blog comment:Mineko Charat Lucky/Stop Telling Me What to Build, Thanks/@comment-5589202-20131013172139/@comment-5556439-20131014041828

Sightstone is under normal cicumstances only 100% necessary if you cant keep reliable control of objectives. You can only use 2 of the 4 wards on Sightsone and only 3 of the 5 on Ruby Sightstone, so if your needing to constantly re-ward objectives (IE the enemy has pinks and you cant immediately de-ward) then its a good choice. If not, then other items take priority because your team needs a LoiS and your CD's to be low more than that one or 2 wards near tri-bush.

Also dont forget that if the enemy team has someone like Kha/Rengar or LB that constantly maneuver AROUND  your team to try and nab a soft target warding choke points would be worth picking up sightstone as it would give free vision to those areas quickly.

But yes Sightstone is fairly overrated and is only 100% necessary under certain conditions.