http://www.davewilson.com/home-gardens/backyard-orchard-culture/photos/multi-planting

scroll down and you will see 3 fig trees in one hole!  

I have 4 figs
I put them like pairs, more space than that though.

Hi Grasa,
Here we call that a fruiting hedge. The idea is to block the sight from outside to inside, and thus you give the trees less space and keep them smaller and in a compact form.
You then need to keep on trimming to let sun reach each tree. Trees are shaped to cordon or espalier .
In a garden I saw someone do that with fig trees, but normally people would use apple trees or pear trees in my area.
As for fig trees the main problem is node spacing. The strain used in the one I saw seemed to have big inter-nodal spaces but still looked exotic .
My back fence starts to be crowded with fig trees and in some way will end as a fruiting hedge of fig trees .

I plant my regular fruit trees sorta like that, but close together in a line. DWN has great pruning videos.

I wouldn't do that with my figs here since if they die back one might overground the others if it's more vigorous. Good choice for those in warm climates though who are less concerned with maximum fruit production.

I love DWN's videos. I do some high density planting but love to watch the pruning vids & orchard tours. 

My father used to say that figs like to be planted in pairs to produce better.