We live in the era of open sources. It relaxes and we start to think that our ideas presented in our software are not so important and not so valuable. Say, there is no point in hiding them.

Do not succumb to tricks! Large corporations can afford to open their source codes. Disclosing their source codes would have almost no impact on their revenue nor earmark. Be sure to remember that the source code itself is often not what keeps the value of a corporation put forward. If you got source codes of iOS system you will not be able instantly distribute an iOS clone system and could not provide good support for it. The code is just a small piece of the final product. But it is a very important piece.

Sometimes small teams of software developers have no other values besides their intellectual property and innovation ideas. Do not disclose them otherwise you will be left with nothing!

You may argue that the main importance for companies is the data stored in their databases, not the source code at all. The writing the source code is a boring monkey business and you can find such code by googling as an open source project.

Absolutely not serious reasoning. It is a wrong way to mix up significance of unique innovative algorithms presented in your software code and encrypted protected data in your database.

Obfuscate your code to make it even if more difficult if not impossible for hackers to understand. Also it makes sense for software comprising a large customer base when you do not want competitors to have much knowledge about your distributed software.

It is obvious that is impossible to make .NET managed code un-hackable by obfuscating it.
Doors do not stop houses from being robbed, however they do make it harder. Someone has to really want to rob a house rather than an average hooligan just wants to hanging around the house. Obfuscation makes it harder to steal the code. A code-thief that really wants it will still do it, but it will stop an average hacker.
There is a testimonial about Skater .NET Obfuscator written on Microsoft marketplace below.