Falls in real house prices are not as rare as many people think.
The falls can happen over the better part of a decade, and are not necessarily a short sharp drop with a rapid rebound.
Refer to
http://www.econ.mq.edu.au/research/2004/Abelson_9_04.pdf
Some examples from Table 2:
Real house prices in Melbourne fell by 21% between 1974 and 1982
Sydney had a 17% real drop between 1981 and 1985.
Perth's fall was 26% between 1970 and 1987 (although there was another boom and trough in between).
One difference now is that in those years inflation was around 10% or so, meaning that house prices could rise by (say) 5% but that was still a relative drop as everything else (including wages) rose faster.
Today, if houses grew by 5% less than inflation, that would mean some absolute drops. This would spook some and lower confidence, especially those whose strategies are based on high capital growth rates (eg agressive -ve gearing). Whereas those whose strategies will succeed with either zero or CPI-only growth rates will still do OK.
Those who buy what I call 'commodity houses' (ie a. affordable eg <$300k b. on good blocks in established areas c. below replacement value d. some improvement potential & e. yield >5%) in 2011 should succeed longer term provided they can meet the shortfall in the interim.
There will be difficulties for first homebuyers in these areas, but their place will be filled by others who perhaps can't afford $400k - well located affordable housing should always be in demand. The immediate prognosis for dearer areas (a $600k - $1m house is not a necessity but a luxury IMHO) may not be so promising however.