how often do you see those?  the two shown are quite a long time between…  it wont be slowing down your site if its extremely infrequent like that…  In normal forum usage, I dont even see any queries that just grab all rows in sfposts…  certainly, not something regular… 

even did a quick search (not exhaustive) in the codebase and didnt see anywhere that we do a query like that…  will try looking deeper…