LinkedIn's performance since its intial public offering (IPO) has made investors very happy. 

LinkedIn has almost a $13 billion market cap, and its shares are trading at nearly three times the opening day price of $45.

But in order to keep Wall Street on its side, LinkedIn needs to make a major acquisition sooner than later, Connie Loizos of peHUB reports

Even though LinkedIn logged incredible growth between March 2011 and September 2012 — with its sales growing across all of its revenue streams (premium subscriptions, recruitment and advertising) — it needs to look for external growth opportunities in order to maintain that pace.

Some analysts have mixed opinions about what LinkedIn should do next.

Rick Summer, a senior equity analyst at Morningstar, told Loizos that he sees a day where LinkedIn looks "more like a software company, managing job candidates from their sourcing to managing the candidate inside the walls of a company."

With that in mind, Summer says that SilkRoad, a 10-year-old employee management software company, could be a good acquisition target.

Other analysts say LinkedIn should also consider acquiring these companies:

Monster.com, an employment website

Chinese recruitment site ChinaHR

Viadeo, the world's second largest social network for professionals

Question and answer site Quora

DemandBase, a business-to-business marketing software company

Business advertising startup Bizo

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