In more recent models, this problem may already be taken care of with an aluminum base or, if a wooden base, may not have developed into a problem, yet. In either case, this area will collect water coming down the mast stub (when the mast is lowered), the sail slot, or around the deck collar.
In my case, with a wooden base, the screws fastening the mast step to the base had become loose due to lateral stress and movement from the mast which allowed any water to seep throw the screw holes into the vault below and rot the base on its way. As time went on, the screws got looser and the base became more rotten. The surface stayed relatively dry and I just thought I was just doing good job keeping the water out. But, as I discovered later, trouble was brewing below.
Yes, this problem was discussed in a previous thread a couple of years back and the cause was blamed on the previous owner drilling a hole through the plate to install a grounding cable. Based on my assessment, I believe the previous problem was also caused by the screw holes and not the grounding cable hole. Being aware of the previous problem made me cognizant of the situation which lead me instantly to the cause of the mast inching south.
No matter how dry you try to keep the area, over time rot will develop; it is just a matter of how long. For ease of mind and relatively low cost (<$100), I would retrofit any wooden mast base with the aluminium plate solution. And yes, any water coming down the mast or by the deck collar will collect here and that may be a good thing. At least it is not seeping to any wooden support areas below.
I don't believe the bow sprit disaster was a result of over tightening the stays. It was the result of an undersized bracket. The replacement bracket was substantially stronger. If you look closely at the pictures, you will see the difference. If you have an older boat, make sure you have the beefier bracket. I am sure ComPac will gladly send you one at minimal cost.
Hope this helps,