Short interest can be a powerful indicator. When it's exceptionally high, it's a strong sign that investors are skeptical of a company, and expect its stock to head lower in the months ahead.

Short-sellers aren't always right -- indeed, they're often wrong. But keeping an eye on stocks that are highly shorted can provide insight into a company's business model, and how investors view it. Below, three Motley Fool contributors dig in to some of the most highly shorted tech stocks, including Tesla (NASDAQ:TSLA), Groupon (NASDAQ:GRPN), and Gogo (NASDAQ:GOGO).

Joe Tenebruso (Tesla Motors): Out of all of the stocks I follow, Tesla is one of the most heavily shorted. In fact, more than 25% of its float is sold short as per The Wall Street Journal. Why are so many investors betting against Tesla? I believe it comes down to one word: valuation.

Based on many traditional valuation techniques, such as Tesla's 8.13 price-to-sales ratio (versus 0.45 for Ford and 0.39 for GM), the stock does appear to be richly valued. It seems that everyone from Wall Street analysts, to industry bigwigs, to famed investors like Joel Greenblatt -- and even Tesla CEO Elon Musk himself -- has taken turns in recent months to call out Tesla as being "overvalued," with some going as far as to predict an outright collapse in Tesla's share price.

But even in light of Tesla's richly priced stock, I would be very hesitant to short this business. That's because Tesla displays many signs of a Rule Breaker, including visionary leadership, best-in-class products, and an aspirational brand. True Rule Breakers tend to consistently exceed investor expectations, and it's entirely possible that Tesla surpasses even the current lofty expectations reflected in its share price.

In addition, there's nothing that says an overvalued stock can't become more overvalued; as they say, the market can remain irrational far longer than we can remain solvent. With the limitless risk inherent in short-selling, shorting Tesla Motors is a risk I simply would not take.

Andrés Cardenal (Groupon): Groupon stock has a short interest ratio in the neighborhood of 15.6%, which reflects considerable negativity surrounding the company. Groupon is in the midst of a transformation, which is clearly an important source of uncertainty for investors. On the other hand, there are also some reasons for optimism regarding Groupon's future.

Groupon is moving beyond its traditional business model. The company wants to be considered a global marketplace that can be accessed from any device at any time, not just a daily deals service. Management wants to build a different relationship with customers, attracting them to the platform in the search for opportunities, versus the old approach of sending daily deals via email.

The company is increasing its focus on mobile traffic and local deals to make its offerings more effective and convenient for customers. At the same time, Groupon is expanding internationally via acquisitions and building a presence in online retail.

Management has a lot on its plate, and whether Groupon can effectively transform itself still remains to be seen. However, the company seems to be moving in the right direction lately. Total gross billings increased by a strong 31% during the last quarter, while revenues jumped 20% year over year to $925 million. Groupon reported 53.4 million active customers in 2014, a healthy increase of 23% versus 2013, so maybe the company's transformation efforts are bearing fruit.

Sam Mattera (Gogo): More than one-third of Gogo's shares have been sold short. The provider of in-flight Wi-Fi service has been a controversial stock since it went public in June 2013, with many investors doubting the company's long-term prospects.

Gogo isn't profitable and it faces heavy competition, including similar operations such as Row44. Last year, AT&T said it planned to compete with Gogo, leveraging its network expertise to deliver a better in-flight experience. That may have proved devastating, but fortunately for Gogo, AT&T nixed those plans in November. Gogo benefits from long-term exclusivity deals with several major airlines, giving its business model a decent moat.

But there's always the possibility it could be disrupted by technological progress at some point in the future. The FCC has hinted it could eventually allow cell phone use in-flight. It would require investment in new equipment on the part of the airlines, but mobile phone owners could rely on the Internet provided by their carrier, rather than Gogo, at some point in the future.

Given that it is unprofitable, and that its business depends on evolving technology, it's not surprising that Gogo is a frequent target of short-sellers. Even if the shorts are wrong, this may be one tech stock best reserved for speculative portfolios only.