But why are people buying, selling and trading?
Imagine if you bought one bitcoin for Ł1,000 and you knew that it would still cost Ł1,000 in five years (hypothetical, ignoring inflation, etc). How much interest would there be in buying it today?
Probably very little. Most people only want it because they think it'll go up in value, and the only way that happens is if more new buyers increase demand.
That's the similarity with the Ponzi. When new buyers 'run out' the value drops as there's nothing to sustain it, which I think we're seeing now.
Like I said, I'm not shitting on it. Bitcoin will have an upward trend again.