Actually, it is encouraged to use your own devices at my company..

We have an aditional WLan with a slow internetconection for Personal use, with no connection to our company lan.
Checking Emails or the internet on our corparate pcs is an absolute no, but for this we have the wlan. And as surfing with a pda or a handy isn't this much fun, most time its just a fast check for mails..