Comment by Scott
"Yes this is correct. The shared user base feature is the one to use.
However, if the sites get very popular and you need to separate them all onto different servers, it would be technically possible to set up your own Single Sign On using Q2A itself."
If there are many Q2A subdomain then it is better to use separate db for every site. If one of the subdomain is performing very well then you can move only that site to high performance server.
Also if any one of site is not doing good and owner want to delete then it is easy to disconnect.
Imagine if there are 15-20 subdomains, using single mysql db will be mess.
@Scott, pupi1985, could you please implement Single Sign On using Q2A or provide solution here so that I can test and you can integrate in next q2a version.
It will be helpful to create Q2A network sites.