I was working on a WCF web service that is hosted by SharePoint 2010 that provisions a users My Site and I kept getting this error message when trying to run the service:

Updates are currently disallowed on GET requests. To allow updates on a GET, 
set the 'AllowUnsafeUpdates' property on SPWeb.

In searching the issue, I found a workaround on the MSDN forums that works quite well: set the current HttpContext to null. When the current HttpContext is null, SharePoint does not know that the request was made during a GET request.

[csharp]// Save the current HttpContext to a variable to reuse later
var context = HttpContext.Current;
var serviceContext = SPServiceContext.Current;
var userProfileManager = new UserProfileManager(serviceContext);
var userProfile = userProfileManager.GetUserProfile(SPContext.Current.Web.CurrentUser.LoginName);
if (userProfile != null)
{
if (userProfile.PersonalSite == null)
{
// Set the current HttpContext to null
HttpContext.Current = null;
userProfile.CreatePersonalSite();
}
}
// Reset the HttpContext
HttpContext.Current = context;[/csharp]

I found this extremely helpful and wanted to share.