Interestingly enough there's another implementation of echo on its wiki page, which is as succinct and simple as the Unix V5 version:

http://en.wikipedia.org/wiki/Echo_(command)

I wonder if, like a "Hello world" program, some of these simpler utilities might not even meet the minimum level of creativity to be eligible for copyright, so complexity was added - true.c and false.c are the other two examples I can think of; the "true" utility is basically generated by the default code template provided by many IDEs.

There's also a fun story floating around called "The UNIX and the Echo" about what it should do without any arguments, or whether or not it should accept options or escape sequences:

http://stackoverflow.com/questions/3290683/bloated-echo-comm...

The official POSIX definition leaves it implementation-defined, with XSI forbidding options and requiring escape sequences:

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/ec...

It's amazing how much variety can be present for functionality that seems so simple at first glance.