From the Annals of Common Sense- Legalize It

 

 Looking at the facts objectively, the illegality of marijuana is a failed policy. The U.S. spends roughly $8 billion dollars (BILLION) on enforcing the prohibition of marijuana with 88% of arrests coming from simple possession (See this article for more information/statistics). Despite this, the regulations are having a negligible effect on the number of people who consume marijuana. Further, since there is a federal law outlawing marijuana that supersedes any state law allowing medical marijuana, and since the DEA continues to enforce it despite the White House's proclamation they would not interfere with state medical marijuana laws, many people with serious medical issues are not able to get the significant relief that marijuana provides them with. This includes increasing comfort and hunger of those receiving radiation treatment for cancer and military veterans who suffer from post-traumatic stress disorder (PTSD). 

Not to mention the fact that prohibition of marijuana seems to come from, originally, somewhat racist motives. For example:

 Around 1915, right at the height of its popularity, cannabis was in over 100 pharmaceutical preparations and seen as a medicine extraordinaire especially for difficult to treat neuralgia. It was in the early 20th century that America discovered jazz, and jazz seems to have been born with an affinity to the good herb. Louis Armstrong, besides being one of the best Jazz musicians of all time, was a cannabis ambassador and really was the very first cannabis activist. At that time cannabis was still legal. It was available in pharmacies, of course, but also could be ordered from catalogs as Hashish Candy and was commonly passed around amongst jazz musicians as cigarettes (“muggles“).[...]

According to Dale Gieringer [2] the very first anti marijuana law was passed in California in 1913. Dr. Gieringer reports that testimony that led up to the ban included this statement from a California pharmacy official: “Within the last year we in California have been getting a large influx of Hindoos and they have in turn started quite a demand for cannabis indica; they are a very undesirable lot and the habit is growing in California very fast…”
Anti-immigrant sentiment may have started the ball rolling, but it wasn’t long until marijuana was seen as a useful weapon to put the genie of African American civil rights back into its bottle.

The policy is even more nonsensical (see what I did there?) considering the United State's current economic dire straits, since the legalization of marijuana, even if only for medical purposes at a federal level, would allow for the more careful regulation and, more importantly, taxation of marijuana. According to the Cato Institute (re-link):

The potential of the industry as a whole is frequently overlooked. Marijuana is by most estimates a more valuable commodity than corn and wheat combined, with experts estimating its annual value to be between $10 and $120 billion. The employment potential of such a market is enormous. [...] If economic stagnation continues, however, employment and tax waste will become more and more relevant in driving public support for ending Prohibition. Unfortunately, that support may have to increase dramatically before any real ground is gained.

That is a rather large spectrum that the Cato Institute is offering but, going conservative with their estimate, even if the value was only $40 billion, you would probably be looking at, roughly, a $15 billion swing to the government. This accounts for the taxes that could be established on the newly found industry as well as a little under $8 billion that would no longer have to be spent on the prohibition of marijuana (if simple possession was also decriminalized). If the government goes for full legalization (since many feel that marijuana is safer than either alcohol or cigarettes), even more could be raised with excise taxes being added on the purchase of marijuana.

Change is gonna come and the  U.S. government (C'MON Obama, we know you inhaled...) should embrace it sooner rather than later. The vast majority of Americans support medical marijuana and roughly 50% support full legalization. Why not give the people what they want and help refill the coffers/decrease unemployment? Tis a no-brainer, no? Getting ahead of public opinion policy wise (barely at that) seems much better, albeit somewhat less safe, than obstinately staying the course and allowing federalism to take its course as public opinion continues to change. Plus, everyone knows the founding fathers were all about the herb... that's just science.