Paid and owned media are controlled by marketers promoting their own products.
promote v.促进，推动，促销，推销，提升，晋升
翻译：推销着自己的产品的营销者们控制着付费和自有媒体。（注意被动句翻译技巧，翻译成中文后应该是主动句）
For earned media,such marketers act as the initiator for users’responses.
翻译：对于盈利的媒体，这些营销者扮演着用户反馈发起者的角色。
But in some cases, one marketer’s owned media become another marketer’s paid media – for instance, when an e-commerce retailer sells ad space on its Web site.
翻译：但是在一些情况下，一个营销者的自有媒体会变成另一个营销者的付费媒体，例如，当一个零售电商出售其网站上的广告位时。
We define such sold media as owned media whose traffic is so strong that other organizations place their content or e-commerce engines within that environment.
翻译：我们将这种出售媒体定义为自有媒体，这种媒体拥有巨大的访问量以至于其他的组织把他们的商品广告或电子商务引擎投放在此环境中。
This trend, which we believe is still in its infancy, effectively began with retailers and travel providers such as airlines and hotels and will no doubt go further.
翻译：这项我们仍认为在其初期的趋势，事实上始于零售商以及飞行和旅店业的旅游提供者，并且无疑会长远地发展。
修正：这种还处于初始阶段的趋势实际上始于零售商和航空、酒店等旅行服务提供商，并且无疑可以走得更远。
Johnson & Johnson, for example, has created BabyCenter, a stand-alone media property that promotes complementary and even competitive products.
翻译：例如，J和J已经创立了婴儿中心，一个独立的推销互补甚至竞争产品的媒体。
修正：例如，强生公司创建了宝贝中心网站，这个独立的媒介用于推广互补性产品甚至竞争性产品。
Besides generating income, the presence of other marketers makes the site seem objective, gives companies opportunities to learn valuable information about the appeal of other companies’ marketing, and may help expand user traffic for all companies concerned.
objective n.目标，目的adj.客观的，客体的
appeal n.上诉，吸引力，感染力，呼吁，恳求adj.上诉，申诉，呼吁，请求，有感染力
翻译：除了产生收入，其他营销者的出现让这个网站变得客观，给公司了解关于其他公司的营销号召力的宝贵信息的机会，也可以帮助增加相关公司的用户访问量。
修正：其他营销者的介入不仅给该公司带来了收入，还令网站看起来公正客观，并且使企业有机会获得有价值的信息，了解其他公司市场营销的吸引力，还有助于扩大相关企业的用户流量。