db performance on recent posts

Hi, we display 10 recent posts from across the blogs in every blogs sidebar.
I can see that MySQL logs these slow queries repetedly:

# Time: 111109 15:26:28
# User@Host: dbuser[dbuser] @  [217.25.39.14]
# Query_time: 17.410294  Lock_time: 1.244156 Rows_sent: 0  Rows_examined: 196877
SET timestamp=1320848788;
SELECT site_post_id FROM wp_site_posts WHERE post_id = '186436' AND blog_id = '2317';
# User@Host: dbuser[dbuser] @  [217.25.39.16]
# Query_time: 11.586513  Lock_time: 0.000072 Rows_sent: 10  Rows_examined: 196887
SET timestamp=1320848788;
SELECT * FROM wp_site_posts WHERE blog_public = '1' ORDER BY post_published_stamp DESC LIMIT 10;
# User@Host: dbuser[dbuser] @  [217.25.39.14]
# Query_time: 16.620471  Lock_time: 0.000100 Rows_sent: 0  Rows_examined: 196877

I'm no expert in this are but would you say we have performance issues?

Thanks
Tomas