While most of the data shown relates to U.S. demographics, it's important to note that there are currently over 9,000,000 Australian Facebook users, over 53% of the total online population.
In January of this year, Australia was in the top 10 countries with the largest populations of Facebook users, but we've been outstripped by emerging markets in South East Asia, Indonesia and the Philippines, primarily.
Nearly 33% of Facebook users in Australia are over 35.
A recent report on SFN Blog showed that women aged 55 and over are the fastest growing Facebook demographic.
In fact, from April 2009 to April 2010 the 55+ demographic on Facebook showed 922.7% growth! (Source: iStrategyLabs)
Australia's own growth in Facebook seniors has been less sensational, but is also growing massively.
In July 2009 there were 240,000 active users in the 55+ age bracket. As of this writing there are 612,440 over 55s actively using Facebook.
This shows a 155% year on year growth of Australian seniors actively using Facebook.
Hitwise recently uncovered some very interesting data - each age group participating in social networking in Australia represents a roughly equal percentage of the online population:

Image from Hitwise: the changing face of social networks
On Laurel Papworth's similar blog post, she noted that while Australians as a percentage of online population create more content compared to the U.S., seniors are (in general) consumers of content rather than creators:
American seniors use internet more, yet Australians across the board create more content – but there is still a massive growth in the retired demographic getting social here in Australia.
To sum up:
- Over 50% of online Australians use social networking on a daily basis
- Seniors are a demographic segment experiencing massive growth
- Seniors make up approximately 20% of overall social networking activity
- Seniors are in general consumers rather than creators
That last point should be a boon for internet marketers wanting to target baby boomers on social networks.
Anecdotally, both my parents are active internet users who have jumped on the social networking bandwagon at the periphery. My mother uses YouTube on a daily basis to provide her line-dancing practice videos. They are both avid GraysOnline shoppers - in fact, most presents bought over the last few years have been purchased online.
In itself that's hardly evidence of a massive potential market for seniors shopping online, however, I believe there's significant gains to be made in engaging this demographic.

