The recent VU 15.18.0 release notes included the following:
It is now only possible to drop items in your own estates
This change sparked a lot of discussion in community channels, along with much speculation (some of it wild yet entertaining) as to the reasons for the change.
The main purpose of removing the ability of dropping items on the ground in "public" places was to improve performance. Having a large number of low-value items scattered across busy servers was negatively impacting performance for everyone on the server. On some busy servers the effect of "item art" and random litter was very detrimental to performance.
Another concern was security, since we receive quite a few support cases each month where participants (especially new ones) inadvertently drop items on the ground (despite the warning dialog).
We are of course open to creating exceptions for special cases where placing items in the universe is desirable and unlikely to be abused, and we welcome your feedback.