Tiki is easy to host. Just about any hosting company can offer PHP/MySQL hosting.
But what if you want a hosted version with 24/7 support? The hosting company supports the server, not the application.
Tiki8 has improvements in dynamic preferences and System configuration which will permit custom admin panels and make it possible for SaaS service providers to reduce the number of prefs (and thus potential support) available in a given Tiki instance. For example, they could deactivate all experimental features.
Related: FLOSS SaaS