Thanks Brenden, are you able to elaborate on your comment "You can also specify which widgets can be used in which zones by defining that zone to be a widget zone"? I can't see any way to restrict widgets to specific widget zones. I realise widgets can be restricted by site and role, but as far as I can tell once a site editor does have access to a widget they can place it in any widget zone on that site.
Of course for many zones this wouldn't make sense. If I'm right it is essential I find a way to restrict widgets to zones or as far as I'm concerned Kentico is not fit for purpose. I've worked with enough large corporate clients to know that they'll see this as a significant problem. They'll have to rely on trust to ensure their editors use the correct widgets. So I'm hoping someone can suggest a potential customisation to work around this limitation.
To give a simple example, I might define a widget zone on a products landing page where I want to allow users to add spotlights to showcase specific products. This zone has a very clear purpose. Not only is it impossible to enforce this purpose, but it's also confusing for editors to be given so many unrelated widgets to choose from.