From your experience, is there any context where you should not use Sharepoint in an organization?
As SharePoint people we'll probably have a tendency to say No, you should always use some version of SharePoint (could be the free SharePoint foundation or Search Server Express).
But I'd say that you should only use SharePoint if you have some business need which SharePoint can solve and which has a value greater than the cost for implementing SharePoint, which in no way is free (the hardware/software may be something you already have, but the setup, maintaince and training will still be costly)
Trying to introduce SharePoint without a valid business goal is a doomed project.
Sharepoint can be a great Content Management System (CMS), but if you want to make it more of an application server that can become costly in terms of paying programmers to make custom web parts. In my experience it can be used as an application server but it is painful and never quite feels like a regular web app.
I think you're asking the wrong question entirely. What you should be doing is considering what your businesses needs are and conducting research of the marketplace of applications that best address those needs, including open source options.
SharePoint is good at some functions and weak at others. Most larger enterprises run SharePoint with several vendor add-on suites and in conjunction with other content management solutions to address some of SharePoint's weaknesses.
This is queiet interesting topic for me, so here I throw some question into the disussion.
Can you guys give some examples of solving business needs with SharePoint?
For example you have a company, which has let say 20 employees, those employees word outside driving from clients to clients, and you have one secreatry which distrubs the work amongs the employees. Currently for example they use some phones or mails to send a timesheet to who should go to who. Of course the company has some client records etc ...
And that is it ..
In this case would the SharePoint be a solution for improving the work a bit, lilke saying the secretary will just need to add a new document to a document library, the employee enteres the Site, it sees ok there is a new document for me and yeah easy. Then employee could verify the client by checking the client records in SharePoint in a Client list etc.
In this case is a SharePoint valuable solution?
It will not solve that much, and it will cost some money, but it is raw implementation, just a server with SharePoint foundation.
And as i already asked could you provide more clear examples ... SharePoint for small businesses?