I found a logo of a company named Ibbt. As you can see, there is a separation between elements (the shapes in the left). Can anybody tell how to create such effect in Illustration?
The actual fanning looks like layered transparency. Meaning, you maybe start with a rectangle, cut it down to size, and make more on top until you are fully opaque.
I'd look into the Draw Inside feature in Illustrator. That way, you create your fanned look and then cut and paste the shape(s) into whatever shape.
I'll try and expand this answer later, but I hope this helps!
Draw your shape and adjust its transparency.
Layer additional shapes on top of the transparent shape (I just copied and pasted)
Once you're done, select the shape you want to paste your fan shape into and select "Draw Inside"
Now just copy and paste your fan shape with the "draw inside" shape selected.
You should be able to do this with multiple shapes as well by grouping them together before selecting "Draw "Inside'.
Could surely be done with the pen tool and pathfinder tool in illustrator.
It would be much easier to use a layer mask in photoshop however.
That said, if you're creating a new, important logo, for anything other than a one off website, you're better off not taking short cuts and refining every detail of the logo in illustrator so you have it as a vector file for future use. Otherwise, assuming the logo doesn't change and the company doesn't fail, you'll eventually have to redraw it in illustrator as a vector anyhow.