I didn't start with an empty bar, but I started pretty low and worked my way up in slightly larger increments. I actually just got back to Stronglifts after taking some time off to focus on just conditioning (largely borrowing from Infinite Intensity) to prep for a kyokushin tourney. Now that I"m "off season" again, I"m back to 5x5, and I dropped the weights down a fair bit. It adds back up pretty quickly, so I think it's a good thing to err on the side of caution. If you start 30lbs to low on squats, you'll make it up in a couple weeks at most. If you start too high and wreck yourself, or stall out too soon, you may lose more than that.