Today I encountered the same problem as stated in a blog post by Christopher Maish. When activating the feature via powershell the associated feature receiver was not called.
Trying the suggested solution in the blog post drove me to the cause of this problem. When using stsadm I got an “access denied” error.
I did run my script via Powershell ISE within Windows Server 2008.
So the real problem is caused, again, by UAC (User Account Control). When starting the Powershell ISE with “Run as administrator” and executing the script the feature receiver is now called as expected. Even when using Enable-SPFeature!
