I know that every professional thinks their bit of the process is more important than people give them credit for. Designer's don't just colour in wireframes handed to them by the Information Architect. IAs don't just draw boxes and arrows. Copy writers don't just copy-and-paste the company brochure over the lorem ipsum.
Now that I've said that, I must now point out: Developers don't get nearly enough credit.
This may be something to do with the odd confusion that is 'web designer vs. web developer'. In some - and possibly the majority of - agencies, the web designer not only designs what the page looks like in Photoshop/Fireworks/Whatever but also produces the HTML templates, CSS and whatever JavaScript they feel comfortable with (the tutorials at jQuery for Designers probably help, too). In these agencies, if there is such a person as a web developer, they are most likely responsible for moving the relevant bits of HTML into template files, adding in any back-end integration and possibly writing some of the trickier JavaScript. The confusion arises in the other kind of agencies. The kind where web designers make Photoshop files and web developers turn them into HTML. The designer doesn't necessarily need to know anything about HTML, semantics or scripting. Not to minimise the importance of this kind of designer - they'll know a lot about typography, and visual relations, probably quite a lot about user experience and the process involved in bridging the gap between what the client wants to say and how the user wants to hear - but it's this kind of web developer I think doesn't get enough credit.
If you're designing a site with a full knowledge of how it could be marked up, you will naturally - even if it's subconsciously - be marking it up in your head. This will influence your design and not necessarily in a bad way. You might ensure the semantics are just that little bit clearer or you might nudge these bits over that way so they can be grouped with those other ones there. If, however, you design with no thought at all about how this is going to be made, you will, most likely, do some things that you wouldn't otherwise. If your front-end developer can take this and turn it into a perfectly semantic, clean-coded masterpiece of HTML and CSS then apply JavaScript to progressively enhance the heck out of it and still keep it looking like you designed, they deserve to be lauded, applauded, praised and thanked. Publicly. The usual outcome of this situation is that the designer gets asked along to the awards ceremonies, puts it on their portfolio, an article in the Drum, happy. The developer gets a pat on the back from the team leader and asked if they could just tidy up how it looks in IE5.5 before they head home for the night, that'd be great, thanks.
Sure, maybe we just need some better awards ceremonies for geeks. The kind of thing that the agency sales team will be able to brag about to potential customers (as that, in essence, seems to be the point of awards ceremonies) but I also think there might need to be a bit of a change of opinion in the industry. Just as designers don't just colour in wireframes, developers don't just open the designs in Photoshop and press 'Save for web...'.
I hope this doesn't sound too ranty. These thoughts were prompted after seeing a few designer and copy writer portfolios which contained sites that either I'd built or one of my team had built. Writers credited, designers credited, developers (who built some awesome stuff on them, by the way) lost in the mists of time.