The number of teenagers who use Facebook has gone down from 94 percent last year to 88 percent this year, according to a report by research firm Frank N. Magid Associates. The research, which surveyed 1,934 respondents last September, reflected the significant drop in users aged 13 to 17 in the U.S., a further decline from 2012's 95 percent.

According to the survey as discussed by CNet, 18 percent deem Facebook as fun, 16 percent find it trendy, while 16 percent think it's informative. However, when it comes to security, only 9 percent think it's safe and 9 percent consider it as trustworthy.

Adding to the low ratings in security, the decline may also be due to teens no longer thinking that FB is the "in-thing," preferring to use instant messengers such as Snapchat (18 percent), iMessenger (17 percent), WhatsApp (9 percent) and Google Hangouts (9 percent).

"You look at Facebook and you say, 'Wow, something really changed in 2014,'" Tero Kuittinen, a managing director at Magid, told Bloomberg. "If kids are starting to use so much of their daily time on messaging apps, surely it's going to hurt somebody."

The study also revealed a decline in usage in other age groups, from 93 percent last year to 90 percent this year.

The reduced numbers might be an indication of Facebook's dwindling popularity, although it still remains as the favorite social networking site, keeping in its numbers a majority of users. A survey conducted last June by another research firm, Forrester, which polled 4,500 teenagers from 12 to 17 years old in the U.S., indicated that more than 75 percent use it.

"Facebook has been so deeply embedded in the lives of the people that the fade is going to be slow," Bloomberg quotes Kuittinen as saying. "People just start being vaguely dissatisfied and then after a while they stop using it."