I am not a fervent advocate of the strictest copyright possible, I even am a great supporter of the Creative Commons Initiative, since I do believe that we need to rethink the concept of fierce limits for creative work - given the possibilities of world-wide networking, publishing and cooperation.
I think that - as CC aims to do - simplifying the possibilities of utilizing all the works in this immense pool, that the net provides, will result in a much richer creative cultural sphere.

I do not vote for creators to dismiss their rights over their work, not at all. I instead call for authors to think about enabling certain uses of their works without the need to ask them for permission each and every time.
Sometimes this may be a good idea, sometimes not. Sometimes you want to loosen some of your rights, sometimes you want to keep them all tight.

In any case I find it self-evident that, whatever an author chooses to do with his creative opus, this decision should be respected.
If he allows his work to be used on a permissive basis, even better.
At all events the least thing that anyone that (re)uses alien works, is to give credit to the original creator - a matter of course in an academic environment for example. To me it is also a sign of respect.
This is also the only prerequisite for the most liberal of the Creative Commons licenses: BY - By Attribution

This is also a requirement of the GNU Free Documentation License (GFDL), the license that is used by the Wikipedia project. (To finally get to the point)

Recently I have come across several accounts here at Ipernity that use texts from the Wikipedia to "subtitle" their photos. I won't name them.
In hardly any case there is any sign at all to be found, where these texts originate from.
There is no mentioning of "Wikipedia", the authors of this text let alone a link back to the original article.

Despite what I have written in the introduction: this is indeed a copyright infringement.

Every page of the Wikipedia has the following line printed on the bottom:
All text is available under the terms of the GNU Free Documentation License.

It is easy to figure out what simple restrictions apply, when you want to reuse content from the Wikipedia:
Text in Wikipedia [...] can therefore be reused only if you release any derived work under the GFDL. This requires that, among other things, you attribute the authors and allow others to freely copy your work. [...] Small quotations of Wikipedia content, with its source attributed, may be permissible under the "fair use" clause of U.S. copyright law.
(Copyright FAQ)

That is a first summarized hint on what you need to consider when you want to use content from the Wikipedia.

Other helpful pages might be:

or best the GFDL license text.

Generally you need to name Wikipedia as the source of the text, as well as the authors and also publish any derived works under the GFDL.
On a sidenote (but don't rely on this): a "gentlemen's agreement" exists that states that you need to provide a local copy of the GFDL, mentioning it and a link to the Wikipedia article as well as its version history.

I am not accusing anyone of deliberateness or maliciousness in disregarding these conditions. I am also not a lawyer, neither am I going to report such behaviour.
Still I think it is necessary to point this out because it might actually turn into a problem for Ipernity or more probable for the respective person - although I am more concerned with the "social" aspect than with the legal side.

To repeat myself and make this clear: please do spread content that is marked to be used in a permissive way, extend the reach of a culture of sharing and hence advertise this model of a collaborative creativity - but when doing so please pay attention to license conditions and thus show your respect for the efforts of others that have created content you want to reuse.

Please bear this in mind when you want to illustrate your pictures with e. g. some background information from the Wikipedia.