Chinese search giant Baidu.com Inc. (NASDAQ:BIDU) has been fighting a rearguard action lately as competition, particularly from Qihoo 360 Technology Co Ltd (NYSE:QIHU), has taken aim at its preeminent position. Its shares are down 30% from their 52-week high and had been as much as 44% off the peak price, but Baidu is on the offensive again and analysts believe it can regain momentum.

Yet most of its revenue still comes from ads, and with the trend toward mobile computing gaining traction even in China, there's a real worry that its base of support will further wither away. So let's take a closer look at whether Baidu will be able to maintain this lofty price level for an extended period of time.

Baidu snapshot

Source: FinViz.com. N/A = not available; Baidu doesn't pay a dividend.

High steppin' honeys When Qihoo launched its own search engine, it was a shot across Baidu's bow, but most analysts -- and probably more than a few investors -- didn't think much of its chances to assail the industry leader's ramparts. Yet after surging to a 10% share of the market and seeing Baidu fall to 71%, the antivirus software company is seen as a force to be reckoned with. Sohu.com Inc. (NASDAQ:SOHU) is falling further behind in third place, with less than an 8% share.

Yet I don't see Baidu's tit-for-tat maneuver in launching its own antivirus product as being similarly successful -- or meaningful, rather. Despite name recognition that ought to help it move the sales needle a little, it seems like a move that diminishes the search leader's position at the same time as it increases Qihoo's stature. Still, with the growing importance of mobile, Baidu is going to need additional sources of revenue, which explains its new mobile browser, its entrance into the handset market, and the partnership with Apple Inc. (NASDAQ:AAPL) to have its search engine standard on iPhones and iPads sold in China.

Battle of Five Armies Qihoo continues moving further in on Baidu's search turf, with rampant rumors that it is teaming up with Google Inc (NASDAQ:GOOG). In the past, management said it is willing to work with third-party providers like Microsoft Corporation (NASDAQ:MSFT), and it has launched a test marketing of Google's AdSense on its search results page. What once seemed like Baidu's indomitable fortress now looks as porous as Swiss cheese.