Managed code ensures things like buffer overflows are a thing of the past, so long as your compiler is secure. It doesn't prevent against the design flaws that often lead to security breaches, but it's a start. I'll take securing a compiler and design over securing hundreds of millions of lines of code, though, any day of the week.

Edit: As for codecs and such, this is why I like my object store idea. Your codec class would encode to a bitstream like now, but the entire class would be there on disk. You could send the whole object across the wire and so long as they are using the same ICodec (or whatever) interface, it Just Works (TM).