SaaS makes sense. Especially when it comes to groupware (Exchange), CMS (Sharepoint), and financials, yes I said financials, read Quickbooks Online. The only problem is that most companies have been slow to adopt SaaS initiatives because of their unfamiliarity with the idea of not owning software. In turn, investors and software company executives burned from the dot-com error, have been slow to create and develop full-featured SaaS applications.
One hint to all you SaaS providers out there: Give them full-featured apps. Nothing turns off a non-technical user then not having the same features that they had with the in-house application. MAKE THE INVESTMENT!!

