I know this post is 8 months old. But maybe there are still people looking for the answer. And here is is:
open wp-content/plugins/buddypress/bp-blogs/bp-blogs-widgets.php
Look for these lines:
<?php if ( !$counter ) : ?>
<div class=”item-content”><?php echo bp_create_excerpt($post->post_content) ?></div>
<?php endif; ?>
Now remove the loop. It should now look like this:
<div class=”item-content”><?php echo bp_create_excerpt($post->post_content) ?></div>
The widget will now display an exerpt of every blog post.
