Two things: One, you should always consider the performance of an external resource before you include it in your blog template—even if it’s just an image. But for those who like the services that Blogrolling.com provides, including the useful “updated recently” information, consider reducing the potential damage from a service outage. On this blog, for example, I address potential problems with the service by (a) only listing my blogroll on my front page and not on pages that are linked to by my RSS feed; (b) arranging the HTML of my template so that my content loads first and the column containing my blogroll loads next. This is a simple CSS layout trick (well, not so simple—read my post about getting it to work) that not only helps mitigate problems with external services—my content is fully loaded and readable while the page works to load the blogrolls from Blogrolling—but also helps make your page more navigable in screen readers and downlevel browsers.
Second, this is the flip side of the argument I had with Lisa Williams at the last Berkman Thursday Night Meeting I went to. The great thing about the blogosphere is that blogging platforms have a fairly low “lowest common denominator” of features—headline + body + comments + calendar archives + permalinks (+RSS). This means that there is lots of room for innovation by a Blogrolling.com, Technorati, Flickr, or Feedster type service to add additional “missing” features. But because there is no platform that does it all, you have to worry about dependencies on outside services for these functions.
The second point is why I haven’t hopped aboard Flickr yet—besides the incredibly slow speed of uploading multiple images. My photos are too important a part of my site for me to outsource them, and so far I haven’t seen enough benefit from the social aspects of the service to outweigh the shortcomings of being dependent on Yet Another Blog Support Service.