Someone is making a whole region run slowly
Each region in Second Life has limits on how many prims can be rezzed, and how many avatars may be present. Other uses of the region's server capacity include scripts, textures, and sounds.
While there are not explicit rules about how to share these resources (besides prims and avatars), Residents must not do anything that intentionally slows the region, nor anything that "hogs" an unreasonable or disproportionate share of the region's resources. Linden Lab desires that the Residents of Second Life share all simulator resources fairly.
"Camping chairs", excessively large textures, and overly-active scripts are some common examples of "unfair" resource usage in mainland regions. In sandbox areas, repetitively rezzing personal homes, as well as using large numbers of prims for long periods, can be violations. Let us know this is happening by filing an abuse report.
Incidents of unfair resource usage are punished as "Disturbing the Peace"; the first one or two violations result in a warning. If the disturbance continues, or repeats at later dates, the Resident responsible can be suspended for three or more days; or (rarely) eventually permanently banned from Second Life.
On private Estates, the Estate owner and managers are responsible for deciding whether resources are being shared fairly.