Research firm eMarketer has cut its estimated growth for proximity mobile payments for this year in half, from $2.12 billion to $1 billion, according to VentureBeat.com. The firm's October forecast predicted that such transactions would reach $2.12 billion in 2013, but it recently released new figures that downgraded that prediction to just $1 billion.

The analysis applies only to proximity mobile payments, which eMarketer defines as:

...transactions for goods or services made by scanning, tapping, swiping or checking in with a mobile phone at the point of sale. Often characterized as a proximity or contactless payment, mobile payments occur in real time in the real world, and are functionally different than mobile commerce—the purchase of digital or physical goods on a mobile device.

The number of participating retailers and the persistent convenience gap between the model and other payment options are cited as primary factors for the sluggish adoption.

Learn more about mobile payments trends.