Is tagging a post in multiple categories bad for your blog?
Following discussions on the web about reducing duplicate content on wordpress blogs, found out a few interesting things. These are things that you may not notice and may assume is normal on a blog. You may even see probloggers practicing such mistakes on their blogs. Well they are unaware of it..but they sure are mistakes
An example is – categorizing an article/post in more than one category. This practice is bad for your blog as it increases the chances of duplicate content on your blog. So Google recommends (Matt Cutts does) that you categorize articlces/posts only in one category at a time. But I’ve seen Darren Rowse tag posts in more than one category on his blog. See his latest post on page rank today. Here he tags the post into two categories. Video Posts and Search Engine Optimization.
Although I believe that it’s good to tag the posts in your blog to one category, seeing top bloggers practice it the other way makes me think… where’s the line to be drawn?

Then how can we safely go about it?
Ashfame’s last blog post..Adobe AIR platform – How good is it?
so what do u say is the best way to use tags and categories.. ??
so does that mean, as long as your blog is not as big as darren’t perhaps sticking to one category for a post is a good idea?
If you do not use category name in permalinks, using multiple categories is safe.
But if you use category in permalinks then a single post may be accessible from two urls. That’s where the duplicate content penalty comes in as the bots see two pages(it’s actually one) which are mirror copy.
Let’s see what Mani Has to say on this !