Putting down weed fabric is like installing rubber mulch, it creates more of a mess than anything, but is ideal under the right circumstances.

I will use weed fabric if there is a large area that will have no plants and only mulch.  The problem with that is it is only a, "feel good", installation.  Within a short time, weeds will begin to grow among the mulch on top of the fabric, and it will have become useless.  I will reluctantly install weed fabric under that specific circumstance.

I will 100% always install weed fabric when we are installing decorative stone.  This makes sense because it helps keep the stone cleaner, and keeps the stone from sinking into the dirt.  In this case I will recommend it.

I will install it when slopes are part of the landscape.  This is like when installing decorative stone, it makes sense, but not as, "Weed control", but, "erosion control".

I will never install weed fabric when a lot of landscaping is going in, and mulch is going down.  That is a waste of time and money.  You have to cut an x in the fabric to install the plants.  By doing that, you compromise the fabric by putting a x hole in it.  What a mess.  I have declined landscaping jobs before when weed fabric is a requirement among plants and mulch.  It isn't worth the effort.  All you get is that, "feel good feeling".

Why does weed fabric suck?

1. It is labor intensive to install.
2. Weeds will grow on top of the fabric among the mulch.
3. Makes future planting a complete pain in the butt.
4. Makes removing plants a complete pain in the butt.
5. Becomes an eyesore if the mulch gets thin, exposing the fabric.
6. It is not natural, and in the future become nothing more than litter.

Personally I think weed fabric is a scam targeting unsupecting homeowners doing DIY landscaping projects.  Logically it makes perfect sense from the beginning.  It will give DIYers an, "I did it right", feeling of accomplishment.  

Unfortunately most of the time it is just a, "good idea", without the expected results.  Sorry!