The Irvine Co. has bee aggressively buying office properties in San Diego this year. In the last 12 months, it has purchased 1 million square feet of office space. In some cases, the investor has purchased properties at record prices and with all cash. While the buying spree is certainly a telling sign of the strength and future growth of the San Diego market, it also could mean that the company will soon have enough market share to control rents.