Many years ago, probably some time around 1990, a lawyer was sent around my employer (in the UK) to brief all the programmers about the need to include a proper copyright notice at the top of every source code file, including the "©" c-in-a-circle copyright symbol.
We programmers tried to explain that the ASCII character set did not include the copyright symbol, and hence our practice was to use "(c)" c-in-brackets. The lawyer replied that this was not acceptable, it had to be a proper c-in-a-circle, and it was up to us techies to figure out how to do it. Needless to say we let him go on his way and carried on using "(c)" because there was nothing else we could do.
According to Wikipedia the US Copyright office has always accepted "(c)", but it says nothing about other countries. And there are still some countries that are not signatories to the Berne Convention.
These days of course putting the proper symbol in source code is not a problem as long as your programming tools can handle Unicode. But I have always wondered: why was the © symbol so important then, and is it still important now?