I can say here that in some countries there are local (fb) fan groups with many members, they make posts and some times invite other members to support them.
If you 're a member of a big t11 fan group, it's very common to have over 10-15 supporters in every game.
Here, to give you an example, it's about a fb Greek t11fan group I 'm a member.
A guy from the group had a game against a member of another group (but not so big/active) and called friends for supporting.
Opponent knew about the popularity of our t11 group and set the time at 06.00 in the morning
Still there was 23 supporters for my friend and 8 for the opponent
Click image for larger version.  Name: crazy support post.jpg  Views: 53  Size: 59.3 KB  ID: 52034

* I agree that in friendlies there is no reason for supporting (specially if a friend is the guest team). Never do that.
** I don't believe that any number of supporters (even this +15 %) can give more than a 1-2% to the process of the game.