In a long-term forecast that could be worrisome for homeowners and the housing market, RealtyTrac says 21% of the nation's residential real estate markets are seeing warning signs of market bubbles like the one that nearly collapsed the market in 2007 and 2008. The firm says 98 counties, accounting for 62 million residents, are 'bubble targets.' And particularly troublesome were the 30 counties to have both a higher unaffordability rate and higher foreclosure rates than the national average - two significant warning signs that a bubble may be forming. MainStreet's Scott Gamm has details from New York.