Bug 9406768 reminded me on the importance of reading this document before starting to use the product:
“The 11.2 deinstallation utility is removing all the homes under Oracle base if these homes are not using the same central inventory and the deinstallation utility finds this home is the only one registered in inventory.
Workaround: While installing 11.2 products:
Oracle does not recommend using multiple central inventories. Avoid this if possible.
If for some reason a different central inventory is required, use a different Oracle base directory for each central inventory.”
Daniel Westermann's Blog 