You can Create as many Smart Sites as you like for Free.
You can also Delete any Smart Sites you no longer want.
Click on Your Name in the top right corner.
Click on Account Settings.
In the Advanced menu.
Click on the Smart Sites item.
Click on the Menu Icon to the right of your Smart Site.
A menu will open.
Click on the item that says Delete.
A window will open.
Click on the DELETE button in the bottom right corner.