If you're doing an on-premesis to cloud migration of Exchange. Microsoft may give you instructions to run a certain powershell script that converts an user's AD object into becoming a mail-enabled user.
It is called Exchange2007MBtoMEU.ps1
It's one of two scripts they recommend be run. The first script creates an output file that contains the user information that the 2nd script will use to do the conversion.
The problem is the file-writer in the first script does not string-escape the user name. If the user name has a comma in it, then the CSV reader in the 2nd script blows up because it doesn't know how to handle the comma.
Even though I reported the problem to MS, regarding their powershell, I see that they still are giving out with the bugs....
The page with the instructions to use this script is here:
http://community.office365.com/en-us/wikis/exchange/845.aspx
I reported the issue to their support directly and since I had a hint that they really didn't seem concerned, I made a comment on the page on 7 Feb 2013. People in 2014 are still having problems.