It is probably using the official J2ME "apps" for Facebook and Whatsapp. I think it's about as dangerous as trusting any pre-installed app on feature phones and

It is probably using the official J2ME "apps" for Facebook and Whatsapp. I think it's about as dangerous as trusting any pre-installed app on feature phones and even smart phones. About the "absence of a proper multitasking OS", well, that's what many/most non-smart phones have even today. I think my first phone that supported J2ME software would not properly receive messages while the JVM was running, and the handling of phone calls was jerky. If you received a call the application/game would be terminated abruptly, causing any state to be lost. Yeah, that's how most phones worked ten years ago - forget any sort of background tasks, be them Java apps or music (MIDI!) playing. Not all phones were as bad, though: Symbian-based ones, for example had some sort of multitasking IIRC, but these also tended to be more expensive.