Yeah it happens but when it's in the news the whole truth isn't told because the guy complaining usually wants his 15 minutes of fame because the police are big meanies.
But I'll say this, I started almost ten years ago, back then we were allowed to use discretion and judgement. There are procedures now that tell us we shall charge therefore we have no more discretion. I still use it and give people breaks and I choose to deal with the consequences because the laws allow me to do that.
There are however people that are on the jobs that are robots and need to learn discretion etc. and the senior guys see it with the young guys all the time.
As well, with some cops it may not be what you think is a power trip, but a lack of common sense and discretion and it has to do with training. It's the thinking "I see an offense and I'll give a ticket". People perceive it as a power trip but it's really not and yes there are guys on the job that puff up their chests and walk around like they don't stink, and usually over time that's a self correcting behaviour lol