In one of Reason magazine's many retrospectives on Ayn Rand, Shikha Dalmia neatly summarizes a major problem in Objectivist ethics:
This has profound and unfortunate political consequences. On the practical level, it makes it difficult to build a strong and growing anti-government movement based solely on Rand's philosophy, because the older cohort of her followers is falling off on a regular basis. On the theoretical level, Rand's ideas offer no real possibility of developing robust civil society responses to address the needs of those down on their luck. It is difficult to imagine a Randian qua Randian, say, volunteering in a soup kitchen to feed the hungry, or even founding the Fraternal Order of Fellow Randians to provide free health coverage and housing to jobless and homeless Randians. Since misfortune and distress are a normal part of the human condition, a philosophy that offers no positive, private solutions to deal with them will just have a harder time making the case against government intervention stick.
Rand held that charity was not only not morally obligatory, but was immoral because it placed the needs of others above those of the self. I've always found this to be an inadequate ethical premise, if for only pragmatic reasons.
Eventually, each one of us will find ourselves flat on our back and helpless, like a flipped-over turtle. We'll be down, crushed, and broken, and we'll need someone to pick us up -- with no expectation of remuneration. The Objectivist would simply pass by without stopping. And a society wholly comprised of such individuals will degrade over time because members would not get assistance when they need it. Some altruism is necessary.
Of course, a society in which there existed a general social contract -- you pick me up when I'm down, and vice versa -- could be said to espouse selfishness as the fundamental motive.