In the world of venture capitalism, funding comparisons are often drawn between startups and more “mature," publically traded companies. Interestingly enough, in one of the most prevalent comparisons, Facebook (FB), which is possibly the most controversial startup to date, now represents the standard for “old” tech companies. Currently, with the most billion-dollar startups in history, it should come as no surprise that the biggest of the bunch, Uber, is also the most heavily debated. As such, investors can't help but draw comparisons to Facebook.

Although Facebook and Uber offer two very different services, social networking vs. on-demand traveling, historical private funding rounds of each company make for interesting debate.

After its most recent round of funding, Uber is currently valued around $40B, with indications pointing to a future valuation of over $50B. Uber has reached this milestone in just three years (a record for a privately funded startup). In contrast, it took Facebook three years to reach a $1B valuation, and eight years for the company to achieve a $50B valuation. However, Facebook's $50B valuation remains one of the largest pre-IPO market caps to date. Moreover, Facebook’s 2012 IPO, which valued that company at over $100B, was the largest tech IPO in history until Alibaba (BABA) issued a public offering.

Thus, because of their similar pre-IPO valuations, questions arise as to whether Uber will reflect Facebook’s subsequent success. As a side note, it is crucial to acknowledge that Facebook’s IPO was a temporarily short-lived success. With such a lofty pre-IPO valuation, post-IPO Facebook severely struggled to meet expectations. Facebook stock barely closed above the $38 IPO price on its first day of trading, and quickly tumbled to a low of $18 per share over the following months. This is not to discount the fact that Facebook’s IPO raised an additional $16B for the company and its investors, but rather, that lofty pre-IPO valuations often inspire unrealistic post-IPO expectations.

As we now know very well, Facebook’s post-IPO struggles were only transient. The company now trades above $85 per share and is valued at nearly $250B. Thanks to coordinated revenue improvements, in addition to a number of key acquisitions, Facebook was able to meet seemingly lofty expectations and consistently surpass Wall Street estimates.

As for Uber, it’s in a similar boat. Uber faces unrealistic expectations and a number of serious legal obstacles. The company has also refrained from officially announcing IPO plans. Therefore, what’s to stop Uber from adding another $50B to its pre-IPO valuation? As I mentioned earlier, it took Facebook eight years to generate a $50B valuation; Uber has achieved this feat in three years. Investors should remain wary of the Uber's valuation, as it will undoubtedly influence a future IPO. However, as was the case with Facebook, these problems may only persist over the short-term.