RE: http://our.umbraco.org/projects/website-utilities/ucommerce/ucommerce-support/39385-Moving-added-item-from-anonymous-basket-to-user-specific-basket

gistfile1.cs

public override Basket GetBasket(bool create)
{
	// Member is not logged on use default behavior
	if (!Member.IsLoggedOn()) return base.GetBasket(create);

	// Otherwise try and load a basket for the current member, create one if it doesn't exist
	Basket basket = GetBasketForCurrentMember();

	if(basket == null)
	{
		// no member specific basket, check anonymous basket held in cookie
		// (Has basket on the OrderContext class checks for a basket in the cookie of the HttpConext)
		if(this.HasBasket)
		{
			basket = this.GetBasket();
			
			// Set the memberid property on this basket to convert it to a member basket
			basket.PurchaseOrder["MemberId"] = Member.CurrentMemberId().ToString();
			
			// Might need a save here?
			// basket.PurchaseOrder.Save();
		}
		else
		{
			// no anonymous or member baskets, create a brand new one
			basket = CreateBasket();
		}

	return basket;
}