hosts file keeps reverting I run adb shell and append a line to /etc/hosts
using 

echo IP DNSName &gt;&gt; hosts


It works for a some time and then reverts back to having only a single entry for localhost.

Any idea what could cause this?
I am using temp root using VISIONary and I am connecting my HTC Desire HD adbd via WiFi, because it refuses to identify my handset via USB.
No idea why it's doing it, but you could stop it by changing the permissions on the host file to read-only.  

To set a file to read-only, log in as root via ADB (or use the Terminal application and log in as root) and then enter:  

chmod 444 &lt;path-to-hosts-file&gt;

If you need to edit it again later on, enter:  

chmod 644 &lt;path-to-hosts-file&gt;