Is it necessary to attribute Creative Commons licensed art?
There are tons of sites out there with free graphics. You can find a bunch of these sites through freepik.com. It seems that 99% of these graphics use the CC Attribution 3.0 license. I'm wondering what the deal really is with these graphics, and the sites they are hosted on and their licences. I can understand if you are using someone's photo from Flickr or a free web template that you would put some attribution in the caption or footer. But when you are using one vector icon on a website or using a Photoshop pattern as a small part of some larger graphic... are people really expected to attribute that somewhere? I find it hard to imagine that people are carefully attributing things every time they use these graphics. Some of these graphics appear for download on multiple sites and they don't even attribute each other. How do I know that the CC license is real and not just a default license applied to every graphic on a particular site?
My real question is: in the context of using one or two different graphics from these free sites as minor elements in a web or graphic design, is it really necessary to attribute someone, and if so, how do I know who I should really attribute?
It's absolutely necessary to attribute any third party graphics that your site utilizes as specified by the license agreement. Just because there might be other sites out there not properly attributing artwork doesn't make it okay at all. If the icon is so "basic" or "minor" that you think it's silly to give attribution, then consider just creating the artwork you require yourself.
Whether or not the site you're downloading the art from has the rights to distribute the files under a CC license is certainly a judgement call. Does the site look sketchy and contain stock artwork that you can find on more "legitimate" sites for a paid license? Probably best to avoid it. It's in your best interest to protect yourself in these cases, exercise due diligence to confirm the legitimacy of the license so that you have plausible deniability if any issues do crop up down the road.
The biggest re-assurance that you're safe to proceed is if the site lists the actual author (and even better, links to their personal web page). If you can trace the origin back to an actual person, the chances are better that the CC license is legitimate and not just ripped from another website.