Altruism is an interesting trait in that it enables players compassion for those in need without it resulting in a direct benefit for the one helping.
Do you know that terrible compulsion to help someone who is being brutally bludgeoned by monsters and without your help would surely die? Even if they are the opposite faction or a rival guild we often find ourselves helping even though we risk our own virtual lives and might not even receive a word of thanks for the assistance we render.
That my friends is altruism. And altruism is good. Altruism is something we learned a long long time before we even evolved into proper huoman beings because it would allow us to cooperate to overcome challenges that a single individual would not be able to handle.
Altruism allows for the building of society... people that are not altruistic are egotists; An egotist will rarely help you with anything unless it is to their direct benefit.
If we help an egotist our effort is lost. We invested our time and potentially resources in someone that will never return the favor and will most likely never pay it forward either. In the end you're not doing anyone a favor by helping an egotist and you investing time into an egotist is time you didn't invest into an altruist (meaning that you did society a big disservice).
If we help an altruist our effort turns into an investment. The altruist will eventually either help you, be willing to help you if you need it or in some form of the other pay it forward. Our effort is a service to society, we in some way shape or form have helped to make it a better place for everyone.
In both cases the behaviour is ingrained into our brain, hardcoded as it were. An altruist may run away occasionally or make an educated decision not to help but he/she is fighting their compulsion to help and a lot of people will then feel bad for not helping as a result.
An egotist in turn may help someone in the hopes or perceived certainty that he/she will get what he/she wants in return or at least receives some form of payment.
So from all this we can conclude that it's good to help an altruist and not so much to help an egotist (in fact it's probably bad to help an egotist).
The question is how do you really tell an egotist from an altruist?
"Do you have 1g?"
"Can you boost me through RFC?"
Is the person asking an egotist who just wants 1g or a boost for their own benefit or is it an altruist who really needs the help?
The difference between an egotist an an altruist is generally the will an ability to make compromises/sacrifices. If someone asks you for a boost through RFC you should not make a unilateral decision to either help or not you should actively attempt to determine what kind of person you are dealing with.
In order to determine wether someone is primarily an egotist or an altruist you have to determine to what extend he/she is willing to help you in return by displaying a bit of egotism.
"Sure I'll boost you but I need a stack of peacebloom for it. Can you arrange that?"
The egotist in general wasn't really interested in paying for your services and in most cases will move on right away or try and get the boost from you 'before' payment. In some cases the egotist will grudgingly hand over your required payment in which case the net result to society is 0. You helped someone, they refunded your time. You could've invested the same amount of time and gotten your payment so you don't win or lose anything and neither does the egotist (except he got what he wanted and you got something you think is worth what he wanted).
The altruist will at the very least be willing to negotiate the deal and more than happy to trade one favor for another without too much qualm even if it means sacrificing a bit more of his/her time than yours.
"I am sorry, I can't give you 1g but if you pick up herbalism you can go outside of town and get silverleaf and peacebloom which sells quite well on the Auction House"
The egotist will most likely ignore you after this one and move on to their next victim. They were already aware that they could make money by herbing but they had better luck begging it from people.
The altruist on the other hand will generally be either genuinely ignorant of herbalism or will be willing to negotiate some kind of deal thus your teachings will be well-received and will often result in genuine follow-up questions.
While not a perfect test you can indeed find out if people have altruistic inclinations or not. Egotists should be put on ignore as soon as possible, you are not helping anyone by helping them. A society that does not weed out it's egotists is a society doomed to fail in some form or the other. Be it by widespread poverty, creating an anchor through those unwilling to put forth effort for ayone but themselves or numerous other things that can go wrong by giving to those who only consume.
Studies have shown that monkeys generally don't put up with purely egotistical behaviour for too long, just because we have the luxury that we can doesn't mean we should.
Sometimes you can do good by not helping and harm by helping... it is up to us to discern the difference.