The problem with left or right align vs top is related to searching for an item inside a list and correlation to the nearest item.
Example: a user visually scans/searches for a telephone number inside a form and usually scans through the list of Field Names and after finding "Phone Number" he looks to the nearest value. So in this case, having the Field Names on top would make it harder for him to find the information (the list becomes scrambled).
The same with showing "read only" view where the fields disappear, the idea is to have the Field Names nicely aligned so the user can easily search through. The difference will be made by spacing or by adding soft visual details that split the information into chunks.
This becomes less important when the form has less elements like a login form but it still matters.
Also I wouldn't recommend having field information/name inside the actual field.