1. When you don’t need Support. At all.
Example: Google Search.
2. When you are ready to run redundants.
Example: Your free Yahoo Email Account. If something screws up real bad, you just forward all your emails to your Free Gmail Account or your Paid Work EMail Account, and move on
3. When You are the only User for the Software.
Example: All free Apps you download on your phone.
4. When it is just for fun.
Example: All free Apps you download on your Child’s iPad.
5. When you are trying to find out if The Software is worth buying.
Example: Every Freemium Software.
If you are going for Free Software for any other Purpose, think twice.
PS: Social Media is not Software.