Personally, I am interested in reverse engineering, but not at a high-level of ability yet. I do intend to become good, but I am certainly not there yet. This site offers a single place to look for reverse engineering information, so that's a major plus. It's easier to browse questions this way. I don't think much about the reverse engineering tag on stack overflow, so if I had a really interesting question, I wouldn't think to ask it there. Really interesting questions are likely to be a bit open-ended, so I probably couldn't ask it there either.
Also, the more people are talking about reverse engineering, the more people are thinking "maybe I should work in this field". I figure fields with people who want to become skilled, yet are unable to are more likely it is that people like me will make tools to make it easier.
A much more immediate benefit is a sudden influx of interesting questions focused around reverse engineering. I expect some of those example questions are going to be actually asked once the site goes live.
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Another benefit is, if there's a site, or better, multiple sites dedicated to a topic, it seems to me it would be easier to form a community around it. People don't consider themselves part of "the group of people who answer questions related to reverse engineering on Stack Overflow". They may consider themselves a person answering questions about reverse engineering, but they don't consider themselves part of a community that specific.
The reason that's important is because if there's a community around something, people start to collaborate, cooperate, compete, and generally help out. That's less likely to be focused around reverse engineering in a very large, homogenous community like on Stack Overflow, because there's not a focus on reverse engineering.
In fact, I would expect it to be less likely altogether, because there's too many people together, and the amount of contact they have is extremely low. It's fairly random which person who can answer your question does, and there's a large number of people who can. In a smaller site, there's fewer people answering fewer questions, so people are more likely to recognize each other and interact. Even if they don't interact much on this site - very likely - they are caring about reverse engineering and are more likely to seek out or create sites in which a community is formed.
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Summary: More people thinking about reverse engineering = tiny bits of publicity coming in = more people caring about reverse engineering = more publicity coming in = more reverse engineering = more tools, classes, games, etc. aiding people reverse engineering.
Put concisely, my reasons are "more interesting questions", and "more tools for reverse engineering".