There are two main reasons to oppose Socialism:  it is inconsistent with both individual liberty and with economic efficiency. 

The argument about the conflict between individual liberty versus a centrally planned, state-run economy is a more academic exercise, and often one that doesn't resonate with people who don't spend a lot of time waxing philosophical about economic self-determination.  The tendency to sit back and expect the government to take care of things, using money that, since it is extracted from your paycheck before you get it, one never sees is inviting to many.  Also, we all have, to some degree, an appreciation for people who are effective managers and for the very idea of a process being managed by someone knowledgeable (or at least more knowledgeable than we).  It is evident in many news stories — a common question for election or public opinion polls is how well a particular official would or is "manag(ing) the economy".  That the economy is too broad and complex to be "managed" is a debate in the abstract.

Though no more valid than the liberty argument against Socialism, the efficiency and effectiveness argument is much more concrete.  Central planning of an economy simply doesn't isn't effective at allocating resources.  The reason?  Not only is the economy as a whole very complex, but government bureaucracies are inherently slow.  Even if it were possible to transmit all of the information necessary to manage the economy, government agencies are neither trained nor incentivized to move resources to meet demand.  This was especially evidenced in the Soviet Union, where wheat crops were known to rot while people were starving, where state-run stores were notoriously empty of desired items, and where "black" markets thrived.

The failure of central planning hits closer to home with a story today in the Miami Herald and Yahoo News:  Cuba, the Socialist "workers' paradise", is facing a shortage of a basic but treasured commodity:  toilet paper.  According to a state official, "Cuba both imports toilet paper and produces its own, but does not currently have enough raw materials to make it."  So while the state-run stores are stocked up with "mayonnaise, barbecue sauce and canned squid", Cubans who can afford it have to take to the streets to buy toilet paper on the black market; if found, it costs up to two days worth of wages.  Many Cubans are turning to other means — "Chinese and North Korean magazines have been a favorite because of their soft paper", and copies of the state-run newspaper Granma.

The Cuban government is laying the blame for these shortages on "the global financial crisis and three devastating hurricanes last summer", but CNN commentator Fareed Zakaria notes that Cuba's "insane farm policies lead to frequent shortages of fruit, vegetables and other basic food needs, shortages even more serious than toilet paper ... Now, capitalism has its problems, as we have all seen. But at least we're not running out of toilet paper."

While maintaining a firm commitment to Socialism, Cuban dictator Raul Castro has at least made one realization:  in response to the economic troubles over the past year that have resulted in budget cuts and debt renegotiation, he has "has taken various steps to boost output, including putting more state-owned land in private hands and pushing for salaries to be based on productivity."  If the Cuban experience is anything like the Soviet experience, the small amount of land held privately will be significantly more productive than the state-run collectivist farms.  But if he realizes that private agriculture industry is more productive, why stop with only small transfers?  Prior to the Communist revolution, Cuba was the richest, most educated country in the Caribbean.  Under the Castro dynasty, it has crumbled — a fact obvious to everyone except Venezuelan dictator Hugo Chavez, a handful of Hollywood actors, and film maker Michael Moore.

This latest shortage of a simple staple is merely further evidence that central planning of the economy isn't an efficient or effective method of resource allocation, and that's the bottom line.