Mark_Lawrence
Science fiction fantasy
I've only Tweeted a couple of authors a few times, and none ever replied to the Tweets.
I presume it's because they only encourage responses from people they know personally, and/or feel socially awkward online/all the time.
Everyone gets to choose who they interact with online, so I figure if they don't want to with me, so be it - I won't take it personally. It's too easy to read too much into online posting.
Twitter is very bad at delivering tweets - I've found lots of tweets aimed (correctly) at me that never showed in my 'connections'/'mentions' feed.