I'm sure there are many pacers that do a great job but here are some issues I've seen:
- Running uneven splits. In one marathon, the pacer for a time 20 minutes slower than my goal time came flying by me 5 miles in with nobody in tow. Gee, I wonder why nobody is running with you?
- Running up or down hills far too quick. I talked to a pacer at a marathon with a very, very hilly second half and he said he was going to run even splits time-wise, not even effort. I had to verify that he was planning to run x:xx pace throughout.
- Bragging about how much they beat their pacing time by. I've seen pacers bragging about how much they beat the pace time by. OK, good for you, you raced and beat everyone that was looking to pace off of you.
- Pacers bragging about actually making the pace time as they were unsure they were fit enough. At least in this scenario the pacer will most likely run at a reasonable pace for most of the race.