at my work, we started with a no BYOD policy till we had wireless everywhere and it was just needed not just by regular employees but also for guests... of course it's secured and the access is limited but that gave a start for other employees who wanted to have access through their personal devices.. a new policy was created so employees can connect their devices to our wireless but they knew they couldnt get any access to our file servers for security reasons.... anyways. employees started to ask to get their emails in their devices and now, even though we dont really support all these devices (android, ipod/ipad/iphone, tablet, laptop). the need is there and we just need to be prepared and flexible to do it.. why? because all it takes is for one administrator to say something like 'why does X business have it and we dont?' to put you against the wall questioning 'can't you do it?'.
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our policy is very firm on not letting a non-supported device to access our servers and if they dont like it, they can always put a note into the 'suggestion box'..
Cheers