Federal Reserve Chairman Alan Greenspan spoke to the American Bankers Association today [Federal Reserve]  and re-visited the topic of housing. He indicated that any decline in home prices would not necessarily be disruptive [MarketWatch]. 
Some key points from the a new study he co-authored:
- Owner-occupied homes have risen 9% on average annually.
- US housing market is a collection of local market loosely connected by mortgage rates, migration and construction capacity.
- Speculation is largely local, the fees associated with a sale are a formidable barrier.
- 14% of home purchases are second homes up from 7% in 2000.
- Less than 5% of all home mortgages have an LTV greater than 90%.
- The use of piggy-back loans is not strongly correlated with housing appreciation.
- LTV are lower in states with the highest appreciation rates.
These are interesting points made that seem to belie many of the arguments that high risk financing is causing a housing bubble.