No problem as long as it works, but its a designers/developers responsibility to tell them the pros and cons of doing so..

Haven't actually seen it in action, so I'm not sure. As long as it's not destroying the aesthetics and user experience I see no problem with it.

Tacky, totally.

ofcourse it works fine but a car compagny is supposed to look a lit more proffesional i think

I kind of like it when websites use flickr to store images, provided they follow the flickr rules and have the click-through take you to the real flickr page, because it makes all their images available in a very useful form -- especially if they've provided extra stuff like high-res versions and metadata on the flickr page.

In addition, it makes it easier for me to link to the same images, should I wish to do so for some reason, without running into problems with out-of-date links, webservers that get picky about referrer strings, etc.

A professional website should be entirely self-contained and self-hosted, no buts about it.

I don't think a professional site should ever unload responsabilities onto a 3rd party service that they have no control over.

The risk that site elements won't work is doubled.
The risk may be small, but it's twice the risk nonetheless.

Nothing unusual about a company offloading stuff on a third-party. Companies like Akamai and Amazon make fistfuls of cash from it.

No, that seems very inappropriate.

I would like the idea, because visitors can so fav the pictures with their flickr account. And they can create sets, etc. Seems perfect to me. But ofcourse simply links (without showing preview images) would be real cheap.