As millennials continue to drive the future of mobile payment with smartphones, apps, and breakthroughs like PayPal's mobile wallet, check use has declined as much as 49 percent, according to new American Express data.

The 18-24 age group is twice as likely as boomers to adopt new technology, AmEx claims, but there's still one issue concerning consumers across the board: security.

Even PayPal's had privacy concerns over its mobile payment technology and millennial's favorite social media sites are prime hunting ground for identity theft.