I have always heard the only true way to tell how many links you have built is in Google Webmasters. I have been building links to mychemistrytutor.com for over 2 years I had over 3000 not a month ago Today it reads 410
no not really since i rank really well for my target and make a ton of money it was more of a curiosity question
Google Webmaster Tools updated a few days ago. My inbound links count dropped from 1000+ to around 150. I think it happened across the board so it probably won't effect PR, but will be keeping an eye on it.
may be google has changed their backlink checking algo, I am also seeing some decrease in my backlinks :s