the old syquests and cdroms eject the media. ie, the bit that holds the data. not the actual drive electronics.
the drives controller logic remains attached to the IDE/SCSI bus and tells the computer that the media has been
ejected (dismount logical drive)
inserted (read partition table / TOC, and mount logical drives from the index information)
drive is empty (nothing here, all information requests get "media not available" message)
media is ok (read/write operations as normal)
in the case of compact flash, pulling it out of an IDE adapter is the same as pulling the whole hard disk off of the IDE channel - as for telling the computer it is going to be removed, you are actually removing the electronics that would tell the computer that it has been removed.... the computer is left going "huh? wtf?!, i'm sure there was something there, i'm sending request data, and nothing is comming back" - data corruption. if you're lucky.
if you are unlucky, you may have sent a voltage spike down the data lines and blown a controller chip.
PCMCIA does have some "hot plugging" capability, and in this case, i'd guess you aren't booting off of it, so you may be ok. i've never done this so i don't know.
all i do know, is that hot swapping CF cards using cheap IDE2CF adapters is not a good thing. :-)