Housing economists hold varying views on whether real estate bubbles will be widespread and catastrophic or tiny and inconsequential – but many experts agree that subprime borrowers, especially those with adjustable-rate mortgages, are likely to be most affected. John Silvia, chief economist at Wachovia Corp., said during a panel discussion at the National Press Club this week that the biggest challenge in housing will occur in 2006 when a number of subprime ARMs will undergo