Well, first its just smart and probably a bit easier for the staff over at SEW to keep blogging about important topics covering the search engine marketing industry. Second, they use a Moveable Type blogging system (just like the one seroundtable uses), its robust, categorizes well, and a brilliant choice for publishing content for the search engines and users (Read why they decided to use moveable type in the first place). Third, its going to be kept up by Gary Price, Chris Sherman, and Danny Sullivan
Danny mentions the following about the new blog, and the reasoning behind it:
The blog isn't going to replace what Search Engine Watch already does. Instead, it's going to let us better publish some items that may not come to your attention.
Check out the new search engine watch blog.
