How just a little impatience lead to a complete OS reinstall

I use Adobe Air in Ubuntu 9.04 on my EeePC 901 and right now the only Adobe Air app I use is Tweetdeck.
A few days ago I got a message saying that I needed to update my Adobe Air so I saud yes and the update proceeded. But, it seemed to get stuck half way through the update and it wouldn't go any further. As I was doing something else at the time and CPU usage had climbed to 100%, I decided to just pull the plug as I couldn't get the AA update to quit any other way.
But, when I rebooted, I found that Adobe Air wouldn't start and gave a message saying it needed to be reinstalled. However, when I tried to re-install it it told me that it was already installed. Not only that but the Synaptic package manager was completely disabled by whatever was the problem with Adobe Air.
Only solution was to re-install Ubuntu 9.04 without formatting the /home partition.
This went smoothly and now I could finally re-install Adobe Air. However, now Firefox wouldn't work. When I tried to start it, it told me that Firefox was already running and needed to be shutdown before I could start it again.
Additionally, I could neither re-install nor uninstall Firefox.
I found one or two references to the same problem but no solution.
Nothing for it but to re-install Ubuntu again but this time to format the /home partition too.
After this everything was fine.
However, it's not all bad news as I seem to have saved in total almost 2 GB of "bloat" from my Ubuntu install as after I'd gotten everything installed that I needed, I have a total of 2.8 GB free in / and /home whereas this total was around 900 MB before I reinstalled.
Given the small HDD space on the EeePC 901, in my multiboot situation, I'd almost be prepared to recommend a controlled complete reinstall of your OSes every few months just to weed out all of the cruft and unnecessary stuff that builds up unknowingly.
Additionally, having extra OSes on your computer allows you easily to transfer your important files and folders to somewhere safe so they can be retrieved after the reinstall without having to resort to USB keys or the like.