Another notable anniversary zoomed by just before New Year - the 15th birthday of SMS, or at least of SMS over a public network. Apparently the first SMS said "Merry Christmas" - and yes, the author spelt it out in full, as txtspk hadn't yet been invented.

It was sent by Neil Papworth, an engineer for messaging outfit Airwide Solutions, and received by Vodafone director Richard Jarvis. Fittingly, the latter was at his staff Christmas party at the time.

In those days, not many phones were SMS-capable, and many of those that were could only receive messages. You couldn't send messages from one network to another, as the networks didn't have gateways in place - and they didn't have billing systems able to handle SMS either!

So how come the technology has been so successful, to the extent that the operators now receive more than 80 percent of their revenues from SMS?

Part of it was the lack of billing - I knew a large number of people who all signed up with the new Orange network in 1994, because unlike rival networks it didn't (or couldn't) charge for SMS. And having got the taste for it, they carried on using the service later, by which time they could also send messages to their friends on other networks.

It was also greatly helped by having a pervasive client that - usually! - needed no configuration by the user. That's probably why it won't lose out to mobile versions of instant messaging services that still can't sort out how to interoperate properly.

And of course, SMS was mostly spam-free, thanks to filtering by the networks. That filtering has become fairly aggressive in recent years, to the extent that messages sometimes get lost between countries, but it seems most users prefer that to spam. Surprise surprise.

But an important factor was that - even when not free - it was cheaper than a voice call, especially for quick messages and questions that didn't need or merit a long discussion. SMS avoided all the pleasantries that most of us are conditioned to going through on the phone.

In that, SMS is living proof that there are more modes of communication than email, IM and VoIP, something the fans of unified comms need to bear in mind. In particular, people tend to expect IM to be almost as synchronous as voice, whereas SMS tends more towards the asynchronous, like email.

The other thing is that the networks haven't had a big success since, despite the introduction of MMS, mobile data, photo messaging and other services. That shows just how bad people in the industry can be at predicting what'll be a hit with the general public.