Apple shares extended their losses Friday, ending a miserable week for the California tech giant as it surrendered its position as the world\'s biggest company based on market value. Apple ended down 2.36 percent at $439.88, giving it a market capitalization of $413 billion -- while oil giant ExxonMobil rose 0.36 percent to $91.68 with a market cap of $418 billion, to edge into first place. The shares of both firms zig-zagged during the session, with Apple at various points regaining the top spot before falling back. Apple first overtook ExxonMobil in August 2011 as the most valuable company in the world based on the value of its stock. A year later, Apple dethroned longtime rival Microsoft as the most valuable company in history based on the value of its stock at $622 billion. But the company took a bruising this week after Wednesday\'s gloomy forecast accompanying its record quarterly profit announcement prompted pessimism over the tech giant\'s slowing growth trajectory. Apple\'s profit was $13.1 billion on revenue of $54.5 billion in the fiscal quarter that ended on December 29, with sales of iPhones and iPads setting quarterly highs. But despite those figures, investors soured on Apple after it forecast that revenue for the current quarter would range from $41-43 billion and that it would have a gross margin of 37.5 to 39.5 percent, lower than expectations. Analysts remained cautious about Apple, which had seen a meteoric rise last September to over $700 a share but it has slid 37 percent since then. The company shed some $60 billion on Thursday and around $10 billion more Friday. Some express concern that Apple has lost its edge in innovation since the death of Steve Jobs, and is losing ground to rivals such as Samsung, which leads the mobile phone market, and to others using Google\'s Android operating system. Jinho Cho at Mirae Asset Securities said Apple will likely increase carrier subsidies in 2013 and launch \"an entry-level iPhone\" to compete better in emerging markets. \"These moves by Apple should lead to stiffer competition for greater carrier subsidies among smartphone makers, thus driving down handset industry-wide operating margins,\" the analyst said. Colin Gillis at BGC Financial said Apple is facing new challenges. \"While we are incrementally more positive on the stock, we also mention that competition is increasing for the company,\" he said in a research note. \"We see competitors are using price as a lever to get traction in the market. Apple may also run into difficulty posting both the volumes and maintaining its prices over the next several quarters.\"