Could PAA have picked a better time, sure, but they have no idea whether tomorrow will be an up day or a down day on the market. In this market, it is not uncommon for the market to move 2-3%.
PAA had a need to raise equity capital and they did. No use crying over spilled milk. PAA's management team is one of the best in the sector. I would imagine PAA holders would be screaming if PAA had chosen to sell equity at near the bottom rather than near their 52 week high.