I'm just wondering, what is the benefit of having Clairvoyance as a spell anymore when the Blue Trinket exists? I haven't seen it used at all in quite some time (outside of trolls) and I'm curious if it offers anything more than what the blue trinket does or if it is just something that Riot forgot to remove.
Clairvoyance is a pure utility spell. It will not give you any combat bonuses at all, you will use it if you want to play safe and ensure maximum vision. Clairvoyance has a global range and a 60 second cool down (54) with the correct masteries and it is only useless in the wrong hands.
Months ago on my older account I got to Masters in Twisted Treeline, where vision is limited even more so than summoners rift. The summoner spell I always rolled with? Clairvoyance. Only the upgraded Blue Trinket is better, but only because it allows you to place a ward on the target area, but Clairvoyance's range and short cool down is what it has an advantage in.
Highest rank I have gotten to in Summoners Rift was Platinum or Gold(been so long I don't even remember), and even then I rolled with Clairvoyance in 40-50% of my matches. Vision is an important mechanic in the game, but is so underrated. There have been very few games I had where people took time to ward, and in those matches nearly our whole jungle was lit up. In those matches it was rare that the enemy team got a successful gank / invade on us since we knew exactly where they were coming from at nearly all times.
I am blabbering at this point, and rolling with {{summoner:2}} isn't for everybody since it doesn't fit everyone's play style and trolls have made the summoner spell look more trashy than people already think it is.
Even spells like 
has great use, but people just can't utilize them properly
For seeing almost dead people 
To be honest, I'm the one odd person like to use{{summoner:2}} and
together, with
player,
it helps a lot for spy jungler or help own teammate to seal and get the kill low health (if they like to work together with me.)
With this two spell, it lead me to GOLD 3 (:P)
If you won't believe it check my mach history: http://www.lolking.net/summoner/na/42880569
