More rep gives you a bigger e-penis. And I wouldn't say some posts that got rep "didn't deserve it for the post". The things that deserve rep are all in the eye of the beholder.. and if they want to spread the love, more power to them.
Like holyrollers said, man... what exactly constitutes a rep worthy post depends entirely on the person giving the rep. there are no guidelines, really, so its sort of unfair to the rep system for you to hold it up to some imaginary standards... dontchya think?
It all depends, you get more rep from somebody with full green bars (like africantapwater) when they +rep you than if it's somebody with one green bar. It's sort of a way of gaining respect of members that have been around for a while.
Nothing really comes of it, and it doesn't really mean much at all. Someone can always be helpful and respectful and such and not get that much rep, then you can have some asshole that gets dank bud and posts nice macro shots that's got full rep for all the nice pics posted and they can be a jerk to other members outside of that. Rep is a nice thing though, I always enjoy being able to look in my CP and see some new rep from someone, it just shows that someone enjoyed reading my post. For the most part it's a good system though. Most people with full rep bars are regular members who have been around a while and deserve a full bar for their good posts. I try to give it out as fairly as possible and spread the love.
Yep, it is definitely nice to see people appreciate your posts and give rep for them. It is like a virtual high-five...or something.