I'm not sure if anyone is still reading this thread, but here's my favourite example.
The New York Times, published April 24, 2007
Factories, though, are incredibly efficient for building homes, according to Kaufmann. At building sites, the remnants from two-by-fours often get tossed out. By building in a factory, these wood stubs can be saved and used in the next home. Dimensions in the homes, in fact, are selected to maximize the efficient use of building materials.
It also takes less time, because electricians and other contractors can work simultaneously, rather than one after another. In all, it takes about six weeks to build a home in a factory and another four to six weeks to ship it to the foundation, bolt it on and tweak everything. In all, the time to complete a house is cut by 30 percent or more.
Evidently, here a comma is required to prevent us form misreading 'also'.
Wrong reading: There are several reaons why it takes less time; one of them is that electricians ...
Correct reading: Building homes in factories has several advantages. One of them is time. The reason for this is that electricians...
Patrick