Ms. Xu refuses to run ads on her blog even though it's the most influential medium among the three she's involved in.

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But if your plan is to start travel-blogging to earn money, either by selling ads on your blog or by using your blog as a platform for selling your travel books or photography, then WordPress has the best tools.

BBC: Best blogging tools for travellers

He added that Tumblr, as a blogging platform, would likely have to get permission from Tumblr blog writers like him before it could place ads on the blogs and share revenue.

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Now Instagram CEO Kevin Systrom has taken to his company blog to say that Instagram has no plans to turn user photos into ads.

FORBES: Systrom: Instagram Has No Plan To Turn Photos Into Ads

But Groupon advertises on ad networks, which may have placed ads on a variety of NBC websites including the Apprentice, Groupon said in a blog post.

FORBES: Connect