I don't think that either Twitter or Facebook is a good substitute for a blog. I tend to write posts that are hundreds of words long and may incorporate graphics and some text formatting like headings. Twitter is clearly not useful for that, and Facebook has limitations.

The blogging that I do see being replaced by these social sites is the quick post style. Some popular bloggers would dash off frequent quick entries with a few words and an image, or perhaps a link. That type of blog entry has virtually disappeared - Twitter is much better for that.

And actually, my blog traffic is up. Twitter and Facebook are major traffic drivers, because readers will push out links they think are interesting.

I do push my own content to social sites, but in a very minimal way.

Let me expand the question. How has Facebook and Twitter affected forums? Has this forum lost any traffic lately?

I can't speak for this forum's stats, but I think there is certainly interplay between forums, blogs, and social networks. I think forums in general may not get as many really long, detailed posts as in years past. I can recall seeing posts on this and other forums that were nearly mini-white papers. Now, many individuals would put a post that took hours to write in a blog - their own, or as a guest on another blog.

I do think that eventually it becomes a zero-sum game. There is a limit to the amount of time that can be spent posting online, and more time in one medium will cut time in the others.

Not only is twitter or facebook not a good substitute for a blog, a blog is not a good substitute for a real website.

its a wandering herd movement, they all migrated to blogs, and then the non committed ones moved on to twitter and facebook. They will move on to the next big thing when it arrives as well, all the time leaving behind a few who find their home on those platforms.

The faster they grow, the faster they'll fall. Just look at bebo and myspace

I don't think about it so much as one as opposed to the other but think collectively.

netchcken1 - I agree to the wandering herd movement

I think, as a user, to be have a good studious commitment to having all of my data points with which I interact in one place so that I can review them and comment on the ones I want and leave the others alone.

This helps me to better utilize my time. Now, this is from a user point of view and not that of a business.

As a business, I would want to find and utilize the right tool set which will allow me to publish my data in the cleanest most effective way possible to all of the venues I want them on. Whether it be something like an RSS Feed, Friend Feed, Twitter, Etc.

Yesterday I was tracking trends for search on certain phrases in our industry. I noticed a downtrend which started just before the "official recession" began. I then looked at how some sites have fared too. I have noticed that facebook.com has in 2010 been trending downward. [google.com...]

Myspace.com has had a much more negative trend but what's interesting is that youtube.com has been trending downward too. [google.com...]

Now, these are only a few examples which leads me to question to overall use of the many facets of the web. Is search down too? I don't think so. I think what we have is such a fragmented online interface that it's becoming increasingly more difficult to get exact numbers on any one segment. Therefore, it's better to look at the sum of the parts than just the parts.

That's my humble opinion anyway. ;)