From another forum where someone asked a similar question:
There are an awful lot of indie devs who are paranoid about their ideas being stolen. It's pretty rare, though, and generally happens in cases involving big-name developers (such as Vlambeer). If someone thinks there is money in a game concept, they are more likely to clone it. Anything Vlambeer releases is likely going to make a fair bit of money and people know this so their games are cloned in an attempt to "cash in". Just look at the hundreds of Angry Birds ripoffs on the App Store.
Now I'm not saying your game won't make money. However, as it seems it has little to no social media presence thus far, it is unlikely that it would be stolen the moment you started blogging about it. If it got picked up and written about by well-known websites, was tweeted about a lot, etc., then yes, there is a possibility that someone would try and clone it if they thought there was money to be made. But in those cases, if the mechanic is original enough, people know what the original was anyway. Like Nocturne said, sales aren't hurt much. Can you imagine if someone tried to clone Meigakure, the four-dimensional puzzle game, before it's released? Everyone would say, "But Meigakure was doing this first". Sure, some people would buy the clone, but if you had the choice between an original game developed for many years by passionate devs or a cheap knock-off made in a few months as a cash grab, which would you choose?
That's why I tend to regard the fear of ideas being stolen with skepticism. I say, go ahead and blog. Hit Twitter with GIFs, post to gaming sites. Do whatever you can to get your game out there. No one's going to buy it if they don't know that it exists.
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