Facts: When you are invisible, you don't have to worry about jumping off, bumping into trees or going into fire. All you have to worry about is to wait 30 seconds for it to end. The first invisibilty is 250 coins and the second is 500, third is 1000 and the last is 5000.
Although you're immune to obstacles, you have to jump to collect coins scattered above obstacles, and also avoid tripping in turns (swipe too early), falling into the swamp, or bump into trees/stones as they're not effective in invisibility.
Only found in the first Temple Run