From Wiki:

“Backlinks (or back-links (UK)) are incoming links to a website or web page. In the search engine optimization (SEO) world, the number of backlinks is one indication of the popularity or importance of that website or page (though other measures, such as PageRank, are likely to be more important). Outside of SEO, the backlinks of a webpage may be of significant personal, cultural or semantic interest: they indicate who is paying attention to that page.”

So have you ever build your empire with this technique of exchanging links? If so, how do you let know whether later on your buddies will remove your links by mean or chance?
I was always coming to check those links to my site manually every other month just to see that it was so s*cking hard! Here I am sharing with tools to help do this auto backlinks checking a heck of avoiding the troublesome:

1. www.seitwert.de (German but perfect)
2. www.backlinkwatch.com
3. www.linkDiagnosis.com
4. www.backlinkWatch.com
5. www.iwebtool.com/backlink_checker
6. www.checkpagerank.net

Also if you're using Google analytics on your site you can go to webmaster tools and find the link checker option. This one is extremely useful because it shows you how many backlinks google is tracking - it's always fewer than will show in yahoo. Yahoo includes things like nofollow backlinks that Google ignores so the results will always be higher than your "real" links according to Google.
Of course, if you dont' want Google to know what you're up to with a site, you probably don't want to use analytics.

I guess this list is yet to complete, so share with us what have found to be easier that this?