Besides being able to mess up settings and having access to the personal SkyDrive account, what else might an attacker on the corporate network be able to do when the accounts are linked and settings are shared between work and personal computers? What about an attacker on a sync'd personal computer?
I assume this question is in regards to a bring your own device policy.
The biggest security risk of allowing someone access to link a domain and personal account is the ability for them to offload company files on various subjects (customer data, credit card numbers, corporate plans etc.) to their own accounts and to their personal PC. They wouldn't even need to be able to pull off any serious hacking, you've already given them all the access they need.
If the employee does not have the intent to cause malicious harm, a remote attacker or virus on the employees personal computer would be your second greatest risk. Anytime someone gains access to routes that are only meant to be seen by a device physically inside your network or virtually inside your network (VPN) you run the risk of a remote attacker knowing the IP scheme and naming conventions of internal devices as well as the DNS and Domain Controllers contained inside. They may not see the encrypted traffic but the packet still has a visible route. This allows someone to sabotage your network with greater ease because they know the routes and their targets.
Well, I would think that there are actually very few exploits that they could use on the computers themselves. If they find a vulnerability in SkyDrive they might be able to run malicious software on either computer from any location at any time, but this does not seem likely to me.
A possible attack for them to employ would be to fool you; to wait for you to upload a document, then immediately download it, delete it, inject malicious script into the macros of the downloaded version of the document, and then re-upload it under the same name. If they managed this, they could upload viruses to either computer via SkyDrive, and have their injected script automatically run it. The only other thing I can think of is that they could possibly find out what other computers you are using (any computer downloading from your SkyDrive) and use the same passwords from the first computer to authenticate on the second. This could then allow them to use your corporate computer to MITM your whole company, or keylog credit card info, etc. on your home computer. Is this what you were looking for?