I have no issue with people choosing not to have any ultrasounds... I considered it for our baby. My H was pretty keen though and wanted to know some facts about what I basing my decision on.
In the end we concluded that 'excessive' ultrasounds can be an issue (eg. smaller birth weight) but minimal ones doesn't seem to show a danger. So we ended up doing the 12 and 19 week scans. I'm not into the 'scan every time you see your OB' thing that I've heard some people go through.