Shares of social networker Facebook (NASDAQ:FB) are enjoying envious gains today as they jump to four-month highs. That means that Facebook has rallied an incredible 48% from its low set in September. What's causing today's jump?

A tale of three analyst upgrades
Facebook bulls are feasting on a three-course meal of analyst upgrades. Let's go through each of them to see what's worth munching on.

Topeka Capital Markets is reiterating its buy rating on Facebook shares, while bumping its price target by a couple bucks to $36. That target represents an additional $10 in upside from current prices and is within reach of Facebook's $38 IPO price from which it precipitously fell. The analyst primarily cites Facebook's e-commerce opportunities as having important business potential.

Facebook recently launched its new Gifts service, and as it continues to roll out it could even be a threat to Amazon.com's (NASDAQ:AMZN) dominant e-tail business. While Amazon parses your transaction and browsing history to come up with recommendations, it lacks the social twist that Facebook could provide. As Facebook makes progress in e-commerce, Topeka Capital thinks that retailers will hop onboard its platform as an additional method of distribution.

Bernstein also thinks Facebook is a buy right now, upping its rating to outperform with a $33 price target. The analyst thinks that improved monetization trends of Newsfeed inventory will boost results over the next couple of years. That being said, Facebook still has some notable challenges ahead of it and this is a risky pick, but one that Bernstein thinks is worth it.

Last and least, BTIG also gave Facebook shares an upgrade, but this change was simply from bearish to less bearish. Instead of the sell rating it had previously, BTIG is giving Facebook a big fat neutral. The analyst thinks that ad upside is relatively limited even though it thinks that Facebook will beat fourth quarter estimates.

Facebook's payments revenue isn't doing too well, thanks largely to Zynga's (NASDAQ: ZNGA) underperformance, as the social game maker comprises nearly half of payments revenue. As Zynga continues to flail, so should Facebook's payments and fees segment.

With a unique place on the Internet, it's always been just a matter of time for Facebook to build its monetization engine.

Fool contributor Evan Niu, CFA, has no positions in the stocks mentioned above. The Motley Fool owns shares of Amazon.com and Facebook and has the following options: long JAN 2014 $20.00 calls on Facebook. Motley Fool newsletter services recommend Amazon.com and Facebook. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.