Many of these happen when folks write their replies near simultaneously - either at a point where they haven't seen anyone else's reply yet, or at least not one mentioning the point they bring up.

There doesn't seem to be much that can sensibly done about this - nor, however, does it really seem to be a problem.

There has been discussion of this before at Possible first post syndrome remedy (including a pretty humourous spinoff by ignatz, which alone makes the thread worth a read).

Update: see? This thread is a perfect demonstration of the effect. :)

Makeshifts last the longest.