I know I'm dating myself by throwing this out there, but the comparison is, in my humble opinion, uncanny.  You may recall the movie Real Genius.  There's a scene where the kid goes to class each day and more and more kids bring in tape recorders to record the lecture, until finally he's the only one sitting there listening to the professor.  And of course, the next day the professor has a big tape recorder up at the front of the class giving the lecture so there's nobody in the classroom except the kid.

If you think about it, blogging is very similar.  With Windows Live Writer, or a similar program, I don't need to be signed in on my blog's web site in order to post.  You also don't need to view the blog in a web browser.  There are any number of third party blog readers which can read your blog, because your blog publishes what's called a "Feed", and the reader can extract posts from that feed.  

IE7 in fact, which I've been playing around with, has a feed reader built right in.  So you load up the blog in your browser, click the feed button, and it will detect if the blog is publishing a feed as well as give you the option to subscribe to it.  All your subscriptions are then listed in the sidebar, and become bold to indicate you have unread posts. 

Because a feed reader just extracts the data of your posts from your feed, the reader can rehash the post in whatever presentation format it wants.  So your bitchin' goth theme is lost and so are any ads you may have on your web site.

All is not lost however, as there are folks jumping on the bandwagon to get advertising into your feed, regardless of the reader you're using.  Text-Link-Ads is one of those folks, for example. 

I'm not sold on purely accessing feeds via a reader, since some blogs post more than just their blog on their site.   But nor do I like visiting every blog manually in my browser.  I suppose you can always visit the blog itself while you're reading the latest post in your browser to see if it matches up or not.  I guess different strokes for different folks - publish in as many forms as you can and let the masses decide what their own preference is for accessing your content.