i think theyre really fun, and definitely a good idea - depending on the story.
a good example is bittie in check please!, because its set in college with lots of domestic shit we dont see, that we can hear about. its also, i think (i dont read it), set up as the character vlogs his life, so it makes perfect sense.
but then, say, it wouldnt really work for a high-fantasy serious comic. usually. i dunno, if you could pull it off, a twitter where the MC complains in realtime about these stupid fucking monsters and a stupid bloody curse and these complete wankers and their stupid swords, thatd be fun. but my brain gets caught at the 'this character has no idea what twitter IS' barrier. maybe most people dont care abt that.
tldr: cool idea, great extra content for fans, great promotion method