When is two too many? [standards]

One statement often repeated in the standards world is that one standard is good, but two standards are bad. I've heard this statement lately, and take exception with it. I don't disagree that one standard is usually better than two or more, but that doesn't necessarily make two or more standards bad. Good examples of multiple standards that work are modem standards. There is the old, reliable 300-bps modem standard. I don't know about you, but I don't use it. I use the V.90 56-Kbps standard. In fact, there are many modem standards. If we didn't have many, we would still be using 300 bps. There are many other examples of multiple standards. But, you may say modem standards aren't a good example because each improves on the previous one.