What makes a logo iconic?

I am currently a BA (Hons) Graphic Design student, and am required to compose a 6,000 word dissertation - the subject of which I have chosen is "What makes a logo iconic?: It's colour, symbol or simply its budget?". So, I was wondering if in order for me to gain an understanding of others views on the subject, if you could possibly leave your views, discussions or comments on the following?:

Logos...we see them almost everywhere - on billboards, television advertisements, the Internet, newspapers and magazines to name but a few - but what exactly makes a logo iconic?: its colour, symbol or simply its budget? Is time an important factor? Without a large majority of the public seeing the logo, how can it reach its full potential?

I would really appreciate your help and time, its much appreciated :)
I think an iconic logo is when it ticks all the boxes without overcomplicating matters. Its just simple, but COMPLETELY works.

There are too many brands and identities around today that try too hard to try to explain what they are there for.

It also stands out from its competitors by pushing everything else aside.

Originality with simplicity.
When you look at iconic logos you will notice that they are simple, have a stong colour identity attached to them (Cadburys, Virgin, MacDonalds), stand the test of time (but may have been modified - Shell) and don't have drop shadows, gradients and other 'tricks of the computer'. Most designers will start working in mono before using any colour - the logo has to work on many different levels and sizes. Compare them to really 'naff' logos and see how they differ.
you need to work out what 'iconic' means first. And I'm not sure it's about how well designed the logo is. For me, it's more to do with how long it's been here and how recognisable it is. It so happens that most of the logos that fall into that category are pretty well designed too. But I'd venture that the Virgin one isn't particularly nice. Or the golden arches for that matter.
For me, an iconic logo is a logo that within seconds you know who's brand it belongs too. e.g. nike, adidas, mcdonalds, apple and facebook for instance. They are ALL simple, use no gradient tools and dont over complicate things. They let the viewer know whos brand it is within seconds and to the point.
Yes - you should define Iconic first. . . .dictionary definition below

ICONIC - of, pertaining to, or characteristic of an icon.

ICON - a picture, image, or other representation.
- a sign or representation that stands for its object by virtue of a resemblance or analogy to it.
- a picture or symbol that appears on a monitor and is used to represent a command, as a file drawer to represent filing.

But basically you are looking for a logo that represents a brand and is instantly recognisable in the market - the Nike swoosh doesn't need the word Nike to be recognisable, everyone knows the golden M represents Macdonalds without the word, Cadbury purple (think of the gorilla drumming) and everyone thinks of chocolate. . . etc
Agreed on all points above.

Particularly that a truly iconic logo should be able to work in mono, and not rely on trickery and effects to present itself.

A truly iconic logo can be placed on pretty much anything, and hold its own. The smallest little mark at the corner of a 50ft billboard, bled off a page showing just hints of the mark, anywhere.

Great icons become ingrained in your sub-conscience so deeply that you can see just a corner of a logo and know what it is.
The edge of the 'golden arches', the end of the 'swoosh', we know these logos so well we don't even need to see the whole thing before we know what it is!
Thanks to everyone for your helpful feedback, its very much appreciated :icon_smile:

Please, to those of you who haven't commented, feel free too,

Thanks again :icon_biggrin: