Warren Buffett's company, Berkshire Hathaway (BRK.A 1.37%) (BRK.B 0.86%), can't seem to get enough of Occidental Petroleum (OXY 3.90%). The conglomerate recently purchased another 8.9 million shares of the oil company for $405 million. Buffett's company now owns over 264 million shares worth almost $12.5 billion, totaling more than 28% of Occidental's outstanding shares. Here's a look at the likely factors driving Berkshire Hathaway to scoop up so much of the oil stock and some things to consider before you ...