Whilst system admins do have "the keys to the vault", in order to use them they need to have control of a user account on the target machine with the appropriate rights to the local machine. If all you have done is join a wireless network and not downloaded any plug-ins or background apps. then its highly unlikely this is the case.
When joining the network you will most likely have been challenged and accepted some form of either terms and conditions or acceptable use policy which will probably have had some form of monitoring notice. These are usually so widely defined that they allow them to monitor anything from the data you are drawing down and sites visited through to video streaming - all in the name of protecting themselves and those around you from anything you may do. (Lets face it if you were in a hospital bed and the patient in the next bed was showing the outside world the inside of the hospital with their web came you wouldn’t be hugely impressed would you...)
So best advice is disable the web cam & microphone, make sure the general user account is low complexity and has minimal rights over the local machine to do what you need it to now (unlikely you will want to install new software, remove programmes, disable AV, add new hardware etc). If you have programmes in the start-up folder then remove then to stop the machine polling - progs like Skype and the like will poll for data continuously and keep pinging devices attached like the web cam. Also check the relevant folder in the OS to make sure no unrecognised user accounts are present in there and if they are - delete them and use the tools available to monitor what afoot on the machine (task manager etc).
As noted above, most technology professionals don’t abuse their rights over their networks and associated network assets - however this doesn't mean its not possible. When the dust has settled though, almost all examples of breach of security on a personal computer are attributable to it still being in the state it was when it came out of the box...the same is true for home wireless routers..most are unsecure and retain the 192.168.....IP range as well as the default admin/password combination....
