When you develop a WordPress theme for a client everything is perfect until you deliver .
I mean, for little to stop " playing "the customer is almost always the temptation to add widgets and little to be excited, too, and eventually add destroy the structure.
And you can not always get a customer has limited user permissions, because often want at least the ability to add widgets advertising or whatever.
And of course, as you add widgets WordPress infinite so the temptation is great.
In these cases could at least limit how many widgets you can add installing the plugin Limit Widgets that, once installed, provides a configuration page where you set the maximum number of widgets for each sidebar.
Simply, when you want to add a widget more than allowed will not be possible , not " stick "to the bar by dragging. By the way, if anyone had already defined above in more bar around the set appear in red, as a warning.