Shares of Office Depot(ODP 1.28%) are up 8% since activist investment fund Starboard Value LP bought a 13% stake on Monday morning. Starboard CEO Jeffrey Smith believes that shares are "deeply undervalued."

Despite the appearance of a new activist investor, don't expect Office Depot's stock bump to last. Activist investors almost always mean a short-term win for a stock, but long-term success is harder to come by.

Office Depot is behind the curve in many ways, most significantly in terms of online presence. Competition from Amazon.com(AMZN -1.59%) and even Wal-Mart.com (WMT 0.62%)is a killer for brick-and-mortars that are slow to adapt. Office Depot may be undervalued, but in this case, it's for good reason.

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