It would appear nothing can slow Uber down. Despite recent controversy in the press, investors seem confident in the company. After raising money this summer at an $18 billion valuation, the company recently raised an additional $1.2 billion at a whopping valuation of $40 billion for its latest funding round. So in just six months its valuation more than doubled. That's pretty rare, industry experts say.

Read More Tiger hedge fund family backs Uber for $100B-plus IPO

But with the huge valuation comes a few potential problems, say analysts, including setting up perhaps-too-lofty expectations for the company's inevitable IPO.

Too big too fast?

"This is a massive step up in valuation in just six months. Folks obviously feel like it's a big market opportunity and feel good Uber will capitalize on it," said Anand Sanwal, founder and CEO of CB Insights, a firm that tracks venture capital investments.

"There haven't been a lot of companies raising billion plus rounds and their pace is pretty remarkable. The sentiment is definitely positive from at least an investors perspective. It will be interesting to see if Uber can grow into this valuation." For now, Uber is the most valuable start-up among all venture backed private companies, and stacks up pretty impressively against public companies. Read More Uber: HK our fastest growing market outside US

There are only 15 U.S. tech companies that trade above a $40 billion market cap, according to FactSet, and their numbers include giants like Apple, Google, Facebook, Oracle and Microsoft. "This is very rare. From your VC, tech standpoint, only Facebook has gotten this high of valuation before going public," said Adley Bowden, senior director of analysis for the venture research firm PitchBook.

But as Uber's value keeps rising, so will the pressure from investors, industry pros said.



Mounting pressure