Standby server startup question - not broken, just curious

Hi all,

I've got 3 PostgreSQL servers in a streaming standby configuration: 1 primary and 2 standby. These have been running great for a long time, and they are all running WAL archiving
as an insurance policy to the stream. My questions relate to when any standby is started up, I always see in the logs that it tries to read a couple of WAL segments that should be
present. What would happen if these weren't using WAL archiving - that is the primary wasn't sending them segments? How many segments is a standby usually looking for (I think I
always see two)? I've also seen that if one of these segments is broken or malformed, that the standby errors on start and often fails to start. Could I just remove the segment
causing the problem? After all with streaming working aren't WAL archives just superfluous?
--
Jay