We started an Open Discussion section on Muktware, where readers can suggest topics for discussion (the idea is to use these discussions as base to create stories ). The second topic was about the target audience of Ubuntu. The OP (original poster) wrote about his own dilemma to pin-point the core market of Ubuntu, which generated some heat. I  think that's an important topic for various reasons. I, being a FOSS/Ubuntu advocate, often come across the same question as the OP was asking. What is the target audience of Ubuntu?

Can We Define The PC/Desktop Market?
Ubuntu faces the same challenges as any other general purpose PC platform would face. A PC it is used for doing so many thing that it's hard to pin-point one use case. In a broader sense it can be safely said that a PC is for someone who wants to use computing power to get something done.

It could be an engineer trying to create a building design using CAD software; it could be an author using text editor to compose his next novel; it could be an artist using software like PhotoShop to create work of art; it could be a developer using it to write codes, it could be a scientist doing complex research; or it could be an average guy using it for playing games, for staying connected with his friends via the web and much more. In a nut shell there are so many things a PC can do.

Ubuntu is not an exception.

Beyond The Desktop
Let's get one thing clear that in this article we are only talking about the desktop market or the typical PC market. Since Ubuntu is based on Linux kernel it has a huge advantage in the markets beyond those of Mac and Windows. Linux dominates the markets such as embedded space, servers, super computers and much more. So if you are looking beyond the PC/Desktop market you can very easily pin-point the target audience of Ubuntu/Linux. In fact these are the 'core' markets are Linux with very low or no presence of Windows or Mac.

Coming Back To PC
The challenge, as I stated above, is mainly in the PC segment. So, when we look at the Ubuntu's market it's not that hard to pin-point. Instead of looking at who can use Ubuntu let's see who can't use Ubuntu.

Ubuntu is not for you if:
1. You play the latest Crysis and the likes
2. You are a graphic designer and can't live without tools like Photoshop
3. You are a film-maker and rely heavily on Adobe Premiere/ Sony Vegas Pro
4. You have a Netflix subscription

If you are not any of the above, you are the audience Ubuntu is aiming at. You can do almost everything with Ubuntu that you can do under Mac or Windows. In fact there are some advantage of using Ubuntu -- you don't have to pay for the OS, upgrade, security or other critical applications – every thing comes for free. It comes with a lot of cool applications pre-installed which is needed by a general PC user. There is an integrated software center which allows you to install other apps with greater ease. There are so many advantages of Ubuntu/Linux, which I am not going to talk about today as I would like to keep the focus on the topic.

So, I will define Ubuntu's target audience (I repeat I am not talking about the server space, high performance computing/super computers, embedded space and much more as Linux is already dominating these fields.) as the general PC audience where people may use Ubuntu to do different things.

3rd Party Apps
There are a few limitations as mentioned above and those users can be excluded from the current user-base of Ubuntu. Well, you can't run FCP on Windows and Sony Vegas Pro on Mac, so there will always be programs that run on one platform but not on others, due to demand. That doesn't mean Ubuntu is not targeting those users. Ubuntu teams are working hard to attract 3rd party developers with their programs to bridge the gap. It's only a matter of time that you may be running mainstream apps on Ubuntu.

At the same time it's also possible that the open source alternatives of such apps will become so powerful and popular that you won't need PhotoShop as GIMP will be a superior tool.

The success of Blender, FireFox, Chromium, VLC, LibreOffice, MySQL, Android, Apache, etc has proved that nothing to do with proprietary-ness of the code. Open source development, under focused team, can be far superior to the non-free development.

Ubuntu Takes Care Of 95% Of My Computing
I use Ubuntu for 95% of my work. Only thing that I can't do under Ubuntu is film editing for which I use cheaper Sony Vegas Pro under Windows 7. Yes, I do play Crisis, COD or MoH and always pre-order the latest version on Amazon. So, these are two areas – film-editing and gaming – where I use Windows, but then I treat it more like an appliance -- a coffee maker. I don't use Windows for general purpose computing because I can do everything under Ubuntu.

Hardware Support Under Ubuntu
I think this is the use-case of a majority of users. I admit there are some areas where I have to be careful and one such area is buying hardware. I have to make sure that it works under Linux. Well, then I always do research before making any purchase decision.

This is actually funny as I was building a new PC (to be used as Windows appliance for film-editing) and ordered a D-Link wifi card only to find later that Windows was not detecting it. On the site of the card said it was not supported by Windows 7. When I popped the Ubuntu Live CD it detected the card and it worked fine.

As far my phones are concerned I only have Nexus devices and Google takes care of all the updates OTA. My wife does have the Galaxy 10.1 tab but we never needed Kies to update it. Airdroid does a great job.

So, in my opinion, Ubuntu's target audience is simply the one which wants to use computing power to get a job done.