Out Of URLs
Every so often, someone will get a message to the effect of "Empty URL" or "Out of URL's".
According to the SL wiki, all parcels will have a URL "pool" that is basically 1 capable URL per prim allotted to the parcel BEFORE any prim bonuses applied to the region.
So if you have a parcel that normally supports 100 prims/land impact, but has a prim bonus giving it 150 prims/land impact, it will still only support 100 URLs.
If you are trying to use rental units, vendors and/or dropboxes on a parcel and are getting constant "empty/out of URLs" messages, then you need to either boot the sim (in case it's a temporary problem) or look at the number of prims you have available on the parcel, and compare that to the number of scripted items that need URLs.
Region/parcel "Object bonus" only applies to prims/objects, not URL's.
Thus, it is the specific parcel that the scripted items are on that matters for the URL load.