I think I could make a living selling at the open, rebuying 30 minutes later at a lower price... Rinse, repeat.
I actualy did it several times as a short time play - but in reverse order: bought at the dip in the first hour of trading, sold later in the day or day/two later.
One of such short plays turned out to be a very nice mid-term trade - it kept going down after first hour - and I averaged down during that day and then over the course of several days. It ended up to be a sizable call position, which I sold couple weeks later at a 6-figure gain. The buying was on 01/03, 01/06, 01/09 - before the Detroit Auto show :biggrin: