3 sources of inspiration, and why it's ok to be inspired

I have had quite a time trying to reconcile the difference between inspiration, outright plagiarism and just learning the ropes as a newbie in my field.
The problem is the level of guilt about many places you can find inspiration and how to further a design trend without directly copying.

1. The world around you.
This is the source of inspiration that everyone seems to think is actually OK, drawing ideas from nature, people in their myriad forms and architecture. These are out for all to see and are clearly OK to use, as most buildings are considered "public domain", and people in the street would generally be thrilled to be used photographically or sketched. People love attention. And nature, well we own nature right? So sketching a sunset or flower or taking a picture of the way the light strikes the flowering trees in spring is great, regardless of the fact that they've been done completely to death.
The fact is designers are supposed to only take inspiration from sources such as these, according to design culture. The insufferable guilt that we are not as creative as the top design studios, that we can't pull great designs and innovative ideas out of thin air is the lament of every designer, as the design process is mostly internal and takes years to tweak and lots of work to get it to be Fast enough, Good enough, and Creative enough to be commercially viable.
The top design studios are the top for a reason, and generally have over 100 years combined experience under their belts, while you have a few continuing education classes and a fancy new tablet.

2. Print Media
Print media, as widely disseminated and highly public as it is, generally can be considered fair game once you realize that no one cares about the 4-3 ranch style house you live in and how cool your local starbuck's door struts look at a strange angle. After you feel you've exhausted the world around you(you haven't) you may tend to look to newspapers and advertisements, as well as magazines and perhaps even design publications. This leads to the inevitable grunge stage(newspapers) and the high-impact, high-contrast designs that every designer makes once they discover Vector Art and how easy it is to shit out an amazing piece of art that looks like it took more than 45 minuties to create.

3. Innovative Advertisers
Some advertisers are a rare breed of humorous, intellectual, plugged-in giants who understand the pulse of society and effortlessly insert themselves into the memesphere. Some however don't know what the hell they are doing. It is a dangerous game to copy an established niche-advertising campaign that has already taken off, attempting to ride it's success. All too often you will be caught after the swell of the wave has passed and will end up being exposed as the greasy car salesman you are. This does not stop some people though, and with the right niche, trying to bring something that is decidedly underground out into the light can work with unexptected results.