Condensation - probably - you have another wet body in there with you, and importantly - won't contain the tail wagging in the morning when the tent is wet and you wake up

Bears - I have been told by bear people that dogs cause more problems than they solve. While a bear may be "scared away" by a dog, they're more likely to be scared away by a human. The problem becomes when the bear is not immediately "scared away" a dog can become protective and aggressive when a human should just stand their ground, the dog ends up being a target for a bear (often after targeting the bear itself), and then the human tries to help save puppy. The result is bear on human..

I personally like having my dog with me, but I've only taken him out overnight once - most of the time I'm in relatively serious bear country so I will not take him. I don't think a dog is a good idea in bear country. Take bear spray and read up on what to do instead.

Dogs can both attract and chase away other animals - or the dog chases something you would have left alone. depending on the area you're in you may have to worry about your dog going after a porcupine or skunk and turning what would otherwise have been a benign encounter with a forest critter into something decidedly more unpleasant for both you and the dog.

Understand I'm not saying "don't ever take your dog hiking" any more than I'd say "don't take your kid hiking". just realize that you need to be aware of the environment you're going into and be aware of what your dog might do, and make
some wise decisions. How will your dog react when faced with a rabbit, a skunk, a porcupine, a bear.. where do you draw the line in what you're prepared to deal with the outcome.