It can be a problem. The last time I was at the Grand Canyon, I chastised someone for feeding the squirrels. There are signs everywhere saying don't feed the animals.

He said they're just squirrels.

I got in trouble once for having a bird feeder on my balcony in an apartment - it seemed the brids were messy and pooped and littered seed all over the ground floor apartment's porch and they complained.

I had to stop. I didn't like it, but I was "feeding wild animals" which I guess was technically true.  Nobody wrote a newspaper article about it, but then again I'm not a sympathetic old man - not that I think this guy is sympathetic, but some do I'm sure.

I could at least understand the complaint though. The house I grew up in had a few bird feeders and eventually the vermin moved in and if we opened the back door and turned the lights on to let the dog out at night an army of roaches would scatter.  

Leaving a barrel of peanuts out for whatever comes along is just asking for trouble.