Well gee, I did not know this was considered abuse. It is a common tactic for me on domestic flights. The idea is to not purchase an upgradeable ticket where there is no hopes of getting an upgrade. If the upgrade is not
available with a SWU at time of ticket purchase, it is less than likely to be available at the time a segment upgrade may be used. So a SWU is used to book the ticket and hold a first class seat, then the appropriate
number of hours before departure an attempt to change it to Segment upgrade is made. This still requries an appropriate seat be avaialble, and you are not gaurenteed the ability to simply convert it. Works about 50% of the time. The other 50% you either waste the upgrade, use miles (if you can), or sit in back. The reservation agents seem all to familiar with this ploy and don't seem to object.