Well, the only limits we have are:
- you can't give more than one HP within 1 hour.
- you can't give yourself HPs.
To make it clearer, keep in mind that:
- There is no prizes or rewards for getting x or y HPs.
- We can't make a rank of the "top most helpful users". Even if possible, I don't think we would need it.
- The HP thing is just a way for a member to express gratitude other than posting "thank you".
But, you're still not comfortable with it, just think of it as a Facebook-ish "Like" button.