[qnr]

I'm talking about particularly large chains of transactions (like hundreds or even thousands of transactions within the same day, often with most of them included in just a few blocks).

If they actually need to pay to that many different addresses it would be far superior to make a single tx with multiple outputs.

My first theory was that someone is trying to inflate tx volume and the simplest idea they came up was scripting the Bitcoin client to make thousands of small payments in a row.

[martinko]

It can be just a popular service (hence the high number of transactions) with a standard wallet implementation, ie. one transaction per withdrawal. Yes this is inefficient, but I dont see a reason why to automatically assume that this is an effort to inflate transaction volumes.