I predict old school muggings will make a comeback in localbitcoin transactions. Or a more likely scenario would be more sophisticated malware through apps if our phones start becoming wallets (which is already a trend being set).
There have been a good number of attempted robberies on LBC. There have been a number of reports of people trying to trick them into giving the release code for the funds to be released.
We could also certainly see an increase of robberies at BTC ATMs by people trying to steal the private key receipt from bitcoin buyers.