I cant believe I missed this one ....
The correct answer is YES
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.... and NO!
On the YES side:
1) If you have a dog that has low confidence or low self esteem it can help to build it up.
2) For most dog's it is just another activity to pass time.
3) It is a great way for the dog to bond with it's humans and vise-versa.
4) Despite what dominance theory supporters think, letting the dog win at tug-o-war does NOT make your dog think that it's in charge of you.
On the NO side:
Win or loose, It isn't a good Idea to play these kinds of games with dogs who are fearful of ppl, have "guarding" issues or have an aggressive nature.