This is most definitely improper blog etiquette. It is never anyone’s right but your own to be "outed" online. Many people use a pseudonym on their blogs as a means of privacy. In fact, many people not only use a pseudonym for themselves, but also for their family and friends in order to protect their privacy as well.
What to do about it? Contact the blogger directly about your concern. Stay calm, state facts, and keep your emotions out of it. Ask the blogger to please remove your name and state why it’s important to you. It’s quite possible the blogger never meant to "out" you. In fact, I’ve accidentally posted my husband’s name and my own name on my blog and had others point it out. It may just be an honest mistake, so give the blogger the benefit of the doubt.
In addition, consider the context of the offending blurb. Is it clear to everyone that it’s you (e.g., Your Name at This Particular Blog)? Or is it a story that involves you, but others may not realize it’s you? Neither of these situations makes the mistake right, but the latter may not be as detrimental to your privacy. Just something to consider.
The bottom line is make it clear to everyone (readers, friends, family, etc.) that you wish to remain anonymous no matter who is writing about you. If someone does use your real name, contact them immediately and with tact. I’m sure you’ll have the issue resolved in no time.