I agree with your example but we aren't talking about something worthless or with a negativve value.
There are still buyers for homes today, as price continue to tumble. I don't think anyone would suggest this is a good sign for the price of homes. When prices are falling it's not a good sign. It may not be a bad sign either. It could just be that financially some people are feeling the squeeze of the price decline, and the effect on the housing market will be short term.
I'm in for the long term because IMO I'll get a good return in a year or so. The short term ups and downs are not critical to me. But I'm not about to suggest that price declines are a good sign because we still have buyers.