So I want to open my brand new dictionary site (for example, of course there is wiktionary), where words should be added by users. Should I fill my database a little before going public, even if it is a long hand-making work?
And how content-repository structured sites are becoming popular in general? If they doesn't have content at first — without content they won't be attractive, you know. Isn't it a bit Catch-22?
It is typical example of "blank state" problem. Yes, you should definitely populate you site with content. You can use some payed users to use you site during you initial advertising period.
There's nothing wrong pre-populating a site with content. I'd be careful about blowing a lot of money paying people to generate content. That's not sustainable, and those users may behave differently than your real users (in a bad way).
If the amount of content needed is small, do it yourself. You get consistant quality, and will likely learn a few valuable lessons. Specifically: If you expect people to create content for your site, it's great to walk in their shoes and develop a good understanding of what that's like.
If the amount of content you need is not small, you can:
The only way to break the cycle of " if there is no content,people wont come and if there are no people,content wont be generated" is to seed the site with content as its much easier and plausible to seed than trying to get people on to the site :-) , unless you have an awesome feature not available anywhere.
Best of luck :-)