Re: Mass delete blogs
Not sure this will be a huge help, but may ease the torture of removing so many blogs.
In /wp-admin/wpmu-blogs.php
~line 309:
$num = isset( $_GET ) ? intval( $_GET ) : 15;
try changing that last value after the colon to a higher one i.e 100, this should control how many rows are displayed per page.
Sadly they haven’t thought to add a select all checkbox so there is the minor pain of having to check each in turn, silly oversight really given it’s such a common thing to code in lists such as this.
Please note this isn’t tested , it works to control the limited number of blogs on my local test installs WPMU 2.9.2 but I do not imply any warranty in following this , test only on local dev site first.
Other than that I would have thought you would need to work at the mysql script level to remove blogs in bulk, but you require someone with greater skills than I to advise on writing sql scripts.
Lastly; it’s odd you get quite so many splogs and makes me wonder if there are any fixes about that you haven’t added to your site.