Online travel agencies (OTAs) are the original digital disruptors - first-generation internet businesses that identified an unmet customer need and created digital destinations that became the first stop for prospective travelers.

Yet the very thing that gave rise to OTAs - the ability to aggregate digitized data to create economical, do-it-yourself travel planning - now threatens to be their undoing.

The biggest threat in travel planning could eventually come from the tech powerhouse that helped OTAs become successful in the first place. After years of quietly building a brand in travel, Google today has become a leading option for travel search, second only to Expedia.