I'd like the visitor to go the the tag page with the most posts (ie the main blog), rather than have to individually visit each blog's tag pages.
What 'each blog's tag pages'? By default (unless something changed in 3.0 that I missed - very possible) there is NO page that lists all your tags. You can make one, but I do not believe this is built in. You didn't activate the SiteWide tags on each site per-site, did you?
On my site theme the tags are listed at the end of each post in the loop (like the front page and category/tag pages) and in the single post (in case this isn't normal).
So on the main blog front page, we have posts from all subsites, in order from most recent to least recent. Each of these has links to categories and tags. clicking these links takes you to :
mainsite.com/tag/tagname or mainsite.com/category/categoryname
On the subsites, on the front page or category/tag/other archive pages and also on the subsite single post pagesthese categories and tags are also listed below the post. Clicking them takes you to the relevant mainsite.com/tag/tagname or subsite.mainsite.com/category/categoryname or subsite.mainsite.com/tag/tagname (except I'm stripping the category base with wp seo)
I've got a news site and often categories overlap: so similar stories in the news, weather, and cyclone sites might all be tagged with "flood", with the tags all pointing to:
mainsite.com/tag/flood from the main site but to weather.mainsite.com/tag/flood fromt the weather site and news.mainsite.com/tag/flood from the news site and cyclone.mainsite.com/tag/flood from the cyclone site.
Now this is OK in some ways, but if most of my flood info is actually on the weather site, but the news site is a much bigger site with better PR overall, then googlers would often find news.mainsite.com/tag/flood ahead of weather.mainsite.com/tag/flood even though the flood archive might not be as useful.
I'd rather they instead found mainsite.com/tag/flood, which would have links to the individual posts from all the blogs.
I'm thinking something like a link on tag pages to the main site tag would do the trick:
Read more about "><?php the_tag() ?> at mainsite.com
That way people can find extra info if they need it, and google will see several subsites pointing to the main site as the authority.
Although I'm using multisite, its not multiuser, and its basically all branded the same so the individual blogs don't matter so much.
Thanks for your input and ideas