seems we are playing another 'both forum' answer search... so, even tho I answered you on the other one, I'll answer here, for the benefit of those with the same question...
only thing people have reported as 'damaged' were on '08-'09 models, which had a little protective 'protrusion' by the drain bolt of the oil pan... it was changed in '10 and up to today's models, to not have that protrusion...
I haven't heard much after they switched pans.. so can't comment on anything else being 'smacked' by a speed bump...
depending how much you lower it, makes a difference on later models possibly..
we have seen some fractured right handlbar castings, where people lowered the front to a point where the fork top rested on the bar castings, but that's all we have so far..
Time will tell as far as the result on the rear quadralink, and it's effects on driveline failures... I suspect we will see some associated to it, but who can really say what caused them. There have been a couple, and I say that toungue in cheek, just a couple, that went wayyy overboard on lowering, and had tires hit the inner rear fender line.. but the company that made those links folded up.. so we are safe... unless someone goes too far.