[Ilgaz]

This thing mainly happens because of multiple administrator users on single machine, drag&drop installs (which unfortunately lives on) and if in case you demoted your account from Admin to normal user at one point.

If you are comfortable with Terminal (in Utilities), do this to see what I mean and root of the issue.

cd /Applications
ls -l
(that is lower case L, not 1)

You will see the owners differs. You would ask 'if this case can be prevented, why doesn't companies/developers use Installer?'. Installer can have some issues that may even lead to data loss under some circumstances and it doesn't currently provide (even in SL) any bonus like MSI under Windows. For example you can't simply say ''repair omniweb'' like you could under Windows. So, drag&drop lives on.

If you keep using a single users account to install/update software or get rid of multiple administrators, this issue will eventually go away.

PS: Don't even try to ''fix'' the owners via shell/utilities etc. It will create some real problems if you don't know how /Applications work. For example, other users could end up not being able to launch software at all. Especially with ACL, it became even more complex to fix.