Apache/Lighttpd Confusion

Recently have been getting some feedback about my current setup where Apache is actually performing as the front-end server and uses mod_proxy to pass static media requests to Lighttpd. The gist of their concern is that what I am doing is idiotic. More specifically, that it is pointless to have the apache threads, fattened by the inclusion of mod_python, conveying information on to the much lighter duty Lighttpd. This seems to be the reverse of the ideal setup.

My first response was that my setup must make some coherent sense, otherwise why would a fairly large number of setup guides use it? (This isn't a setup I have only seen once, but have encountered it in a number of places, some of which you would be forgiven for believing understood what they were doing.) However, eventually I went and read the mod_proxy documentation, and I don't really see how my current setup could result in an efficiency gain over using raw Apache.

But, why does this setup keep getting mentioned at hostlibrary.com and the same article was also posted at linux.com. The mod_proxy system is also mentioned at k4ml.com. The system is also mentioned at kelvinism.com.

So, my question is, what gives? Is my current setup inefficient, and if so, why are so many people recommending it?