Identifying purchases based on amount

[nrd525]

Is it possible to identify what people are buying based on the BTC amount?  This is the kind of attack that would only work if the economy is small, and there are items that have unique prices or are very popular.

I could see this especially being a problem for people on Silk Road.

Or are purchases split into two or more transactions? If so, that would solve this issue.

[edd]

I don't think the economy is that small. In addition, most of us still have the habit of limiting prices to two decimal places.