It doesn't usually require more knowledge. The majority of bioinformaticians that I know are pretty poor coders, and know just enough Perl or Python to count some stuff up an do some stats on it or plot a graph. They have no idea how to set up a server, write maintanable code, design a database well or keep a website secure. Obviosuly there are exceptions, but the majority that I have worked with are junior level programmers with knowledge of biology.