I am sure that as a big gambling site, Duelbits has very strong tools to detect cheat on their website. If they can not detect cheating activities, their business will run out of money soon because cheaters will not stop if they can cheat and get money.
Thats dust amount compared to what Duelbits is making for sure and while there are lots of people using bots to claim those, pretty sure that the number of like and retweets they got on those twitter giveaways are pretty worth it. If a tweet has high number of likes and retweets, the tweet could ready even higher number of impression especially to new unique potential player
I am still not convinced that they get a lot of new users with all these twitter promotions. A lot of sites do the same on Twitter, so it is hard to stand out and while it is a good tool to keep the current users motivated, I doubt it attract new players but I can be wrong offcourse lol. It would be interesting to see numbers on this.
At least they are trying , Duelbits is willing to spend tons of money for their promotions and luring players so this means all aspect are considered , 1 player is enough for them to be added if that is what can be.
but this does not mean they will only focus in twitter area because duelbits had been promoting their site all over internet , and most specially of course in Bitcointalk .
and also this is not only to attract new players instead to also serve their regular players that is also happen active in twitter.