Currently my employer isn't in control of the wiping of my phone, I am.
The admin can also send out the "wipe" command at any time to disallow access to any company data on your phone, with the serious collateral damage of also taking out all your own personal accounts, e-mail, photos, etc.
So maybe you are in control of wiping your phone. Until you're not.
I'm sure they can send out the command whenever they want. But it's not hard to configure a phone to ignore that command.
As an aside, newer Blackberry 10 phones come with built-in perimeters, one for personal, one for work. Connecting the work perimeter allows company to manage data (including wipe) on that side but not touch data in the personal perimeter. On the Android and Apple platforms, there are similar 3rd party solutions available to segregate and manage work partition independently.
In doing so Blackberry made their devices really painful to use for work because you can't, for example, copy a phone number from a work email and paste it into the dialer. It was a stupid idea, they should have stuck to them being "corporate-only" devices. This is a perfect illustration of why locking devices down in the wrong way is counterproductive, because when it gets in the way too much then actively work to circumvent the entire system and not just the bit which is getting in their way (at the simplest level by copying documents to USB sticks, forwarding emails to their personal accounts - I've been in workplaces where both of those were supposedly "banned" with some kind of enforcement but literally EVERYONE did it because otherwise the place would have ground to a halt).
The rather poorly-understood reality is that in a commercial context, the vast majority of information is not really sensitive or valuable. What's more, users will, in general, know which information is and isn't sensitive much better than IT admins - otherwise they wouldn't be trusted not to tell people who they might know socially working at a competitor for example! For information which is not sensitive, far and away the best policy is to be extremely permissive because this enables people to work in whichever way makes them most efficient and engenders trust by treating them like grown-ups.
For information which is sensitive, because almost all the focus is on "zero information leakage" type solutions, it is far too hard to then selectively ramp up controls around it because everyone's product is trying to solve the wrong problem ("keep work and personal information separate" for example). People do this instinctively (eg using encrypted Zip files) but technical support for doing this the "right" way should be far, far better.