Note that everybody can register their own trademarks, too — it’s not just the “big brands” that can do it, but any individual can do it as well. Sadly, to register a trademark world-wide, it’s an insanely costly process. But if you have a very good SL-based business that depends on your brand awareness, which is something that takes months and years to do correctly, thus requiring a lot of investment (money and time!), you should consider registration too. In most countries of the world this is almost always done online, so it’s rather easy to do. If your brand means business to you, it has value; and protecting it is important and worth the expense — specially because you’ll know that any branded item copied by others will meet with instant content deletion by LL (there is no appeal and no discussion).
Of course, when people delete the brand and just copy the rest of the content, things are harder. But some content thieves don’t bother — they know the item is valuable because it shows a brand that people recognise. In those cases, it’s very very easy to get rid of the copied content.