In a sense, then, suicide is an involuntary transfer of well-being from those who love the suicidal person to the suicidal person himself. Involuntary transfers (in certain circumstances, called "theft") are broadly proscribed as unethical. In economic terms, involuntary transfers are suspect because there is little assurance that the transaction benefits both parties on net.
However, there are some circumstances in which the law, as well as economics, favors involuntary transfers: when the involuntary transfer is necessary to right a wrong. One circumstance in which this happens is quasi-contract (also known as unjustified enrichment); when someone receives a benefit at another's expense and it would be unjust to let him keep it without paying, the law makes him pay, even though he didn't agree to pay for it. My perennial example in my contract law class is that your neighbor has ordered a pool to be built behind his house while he's on vacation. The contractors mistake his address for yours and begin building a pool in your back yard; you say nothing, but happily watch the contractors build the pool. When they're done and ask for payment, you say, "nice of you to build a pool there, but I didn't order one!" You'd likely be legally required to pay for the reasonable value of the (un-ordered) pool, because allowing you to keep it without paying would be unjust, especially since you could have easily stopped the process of building.
Another circumstance in which involuntary transfer is legally favored is the constructive trust. When a wrongdoer illegally acquires the property of another (such as through theft), the wrongdoer is said not to acquire legal ownership of the property; instead, he holds it "in trust" for the rightful owner. This is called a constructive trust, and it is a legal fiction that recognizes that an involuntary transfer at some point might be necessary to right a past involuntary transfer. Constructive trust may even affect holders of stolen property who were not themselves the thieves, if they benefitted from the thief's crime.
Suicide, then, is the involuntary transfer of ill-gotten gains. The person who wishes to die was robbed of utility by being born; he is taking back his own neutral "negative bliss" state from those who robbed him of it and their transferees. Even though one's friends and relatives other than lineal acestors did nothing to cause one's birth, they have in essence benefitted from a wrong, to the extent that creating a suffering person is a wrong against that person.
Similarly, transferees of a swindler can be expected to repay the swindler's victims to the extent of their benefit, even though the transferees themselves weren't the thieves.
Ultimately, involuntary transfers (such as thefts and births) may be best prevented by a policy that allows involuntary transfers away from beneficiaries of these original involuntary transfers.