Based on a sample of two, it appears a relatively small percentage (single digits) of registered instant messenger users are actually on-line at any given time. And, if you consider that "on-line" doesn't necessarily mean someone is actually available to receive a communication, the percentages are even lower. That's striking when compared to cellphones, which many people have on for most of their waking hours.
Anyway, here are my two instant messaging data points:
Recently, Skype broke two records. At the very end of March, they reached 6 million users simultaneously on-line and then at the end of April, they reached 100 million registered users. Skype had 6.27 million on-line yesterday mid-morning (EU afternoon), so their on-line users are running just over 6% of their registered users.
Tencent's annual report (pdf) gives statistics on QQ. Tencent Holdings is a Chinese company whose stock trades on the Hong Kong stock exchange. Their QQ instant messenger service runs on PCs and on mobile devices, mostly within China. As of December 2005, QQ had 493 million registered users, 202 million active accounts and 18.4 million peak simultaneous on-line users. That's about 4% of total registrations, but 9% of active accounts.
What's going to happen as mobile devices become richer communications tools that seamlessly combine context-aware availability with live, or near-real-time messaged, voice, text, photos & video sharing? Think the best combination of VoIP services like Skype and mobile phone interfaces like those I discussed in my March Spring VON presentation.
I expect to see early indications by watching Chinese users as, by shear numbers, the mobile Internet beats the PC-based Internet in China. Companies like Tencent started on the Internet side and have only recently focused on mobile value-added services. It will be interesting to see if QQ's percentage of peak on-line users climbs over the next 12 months.