Rebuilding Eden has a great post called Predicting the future, in which he examines "disruptive technology" and issues that could really skew things for long-term investment planning.

Of course, issues such as pandemics (bird flu) and war are on there - but he makes some really interesting observations about energy markets - certainly a key concern after the recent volatility on the oil commodities markets:

The overall point is just how difficult it is to predict market events in the long-term, but to keep an eye on immediate historical events for a precedent (ie, threat of recession in the US due to debt accumulation, etc).

I read a book recently talking about how the great depression was caused in large part because people had borrowed beyond what they were able to pay. He compared that to what is happening today - even said that the realestate market is only as high as it is because of the long term loans that are available.

I think those of us who are planning for the future and living within our means today will be okay whatever the economic sitution.

That's kindof my long term plan in a nut shell.

I find it pretty hard to make long term plans because my life seems to change so much within such a short space of time!
This is my downfall which I know, as i tend to live for today and whatever tomorow brings I'll deal with it them!

I have seen that times are changing faster than those of the Great Depression in America.

One day funds to invest are at your hand, but world turns in such a way that you need to apply the money to common stipends.

I'm a big believer of investing in gold because look at the housing market - things turn on a dime.