That is not at all the case. If you try to solve a problem but only do it partially, no one blames you. If you try to make a profit by benefitting from a problem, then you have some moral responsibility, maybe not for the problem's existence, but for the people you benefit from. So the claim isn't involvement => blame, but profit => increased responsibility, which doesn't seem so outrageous.

The issue of mutually beneficial exploitation is a big problem in ethics[1]. People who say it's OK, subscribe to what's known as the "non-worseness claim", but many don't. That post you linked to is a shallow, uneducated piece that completely ignores the vast discussion on the topic in ethics literature[2].

Another thing is that even with the most generous interpretation, and even if you do subscribe to the non-worseness claim and find it ethically positive, in most such mutually-beneficial exploitation cases, no one is really trying to solve the problem, just to make the best of a bad situation. That is not bad per se, but let's not pretend Amazon is "trying to solve" the problem of homelessness.

[1]: http://plato.stanford.edu/entries/exploitation/#4

[2]: And that is a charitable description. It reads like an article about the motion of celestial bodies written today by someone who is completely unaware that physics has been an active discipline for centuries, and may have a thing or two to say about the subject. I don't expect everyone to be an expert on everything, and it's great that non-experts write about matters they've only recently been introduced to (as this can help others), but I find it hair-pullingly frustrating when people write about something by trying to deduce from first-principles without so much as googling to see if perhaps there has been some serious treatment of the subject before. It is doubly frustrating when it is those ignorant (though perhaps well-intentioned) articles are the ones that get referenced and discussed. It's like those texts actively erase knowledge.