As tools like Facebook and Twitter are becoming part of our everyday lives, retailers know that word spreads like wildfire, and keeping their loyal customers happy is a must.

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Edelman does not believe restaurants are keeping track of how many loyal customers Groupons are chasing away.

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Whether Zynga.com is driving more loyal users or keeping higher engagement is unclear.

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This allowed us to build up a loyal customer base and keep growing while keeping our spend low.

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