AdwXXds - invalid click rate

I have a proper white hat legitimate website of my business and I am advertising on Ad\/\/ords, with moderate success, for about 6 months. I have to say that big G makes a reasonable effort to not to charge advertisers for fraudulent clicks, I must say I am quite satisfied. However, I suspect that my retarded competitors are clicking into my ads, because on some days my invalid click rate reaches 25%! I can see that the same IP is clicking 10 times into an ad within a space of a minute, coming from the very same search phrase. I doesn't bother me much, as I don't get charged for it - I am making money from the business and I am prepared to accept certain level of invalid clicks anyway as I am making money from the business one way or another. I just wondered what your experience is with invalid clicks - is 25% a lot? I don't suppose I can get in trouble because of that, it's not my fault some idiots are clicking my ads 10 times in a row, is it?