"""
The majority of passengers who replied to the Safety Board’s questionnaire were carrying at least one piece of carry-on luggage. Only 25 passengers (6 percent) reported having no bags with them in the cabin. Of the 419 passengers who reported that they carried on bags, 208 (nearly 50 percent) reported attempting to remove a bag during their evacuation. The primary reason that passengers stated for grabbing their bags was for money, wallet, or credit cards (111 passengers). Other reasons included job items (65), keys (61), and medicines (51). Most passengers exited the airplane with their bags.
Passengers exiting with carry-on baggage were the most frequently cited obstruction to evacuation. Twenty-four of the 36 flight attendants who responded listed carry-on baggage as an obstruction. Overall, 37 percent of the passengers indicated that retrieving carry-on baggage slowed the evacuation; however, in five of the evacuations (cases 9, 16, 24, 27, and 32), a majority of passengers believed that the evacuation was slowed by carry-on baggage. Further, 70 passengers and 8 flight attendants reported arguments between passengers and flight attendants regarding luggage.
[...] The Safety Board concludes that passengers’ efforts to evacuate an airplane with their carry-on baggage continue to pose a problem for flight attendants and are a serious risk to a successful evacuation of an airplane.
"""
http://www.ntsb.gov/doclib/safetystudies/SS0001.pdf (page 66-68)