Legal Question in Business Law in California

In general, there's no law against doing what you describe. But it could be illegal depending on the circumstances. (To draw a parallel: There's generally no law against swinging a baseball bat, but that doesn't mean you can legally swing it at another person.)

I can't begin to catalog all the reasons why using an alias might be illegal. One example would be if you use the name of a specific person in order to impersonate her. Another is if you are trying to obtain money or other items of value that people would not give you if they knew who you really are. Yet another -- and this one is reasonably likely -- is if the terms of service of the site that hosts your blog forbid you to use fictitious names.

There are many other possible reasons why using an alias could get you into legal trouble. If you have specific plans that you think could land you in hot water, you may want to consult with a lawyer before you proceed.

Good luck.