Huw (Brickset) has posted a letter from Jorgen Vig Knudstorp (CEO & President of LEGO) to the online community expressing TLG's views on the issue of posting confidential images. I don't think the words expressed in the letter will come as a surprise to anyone. LEGO is a business with competitors who can take advantage of early looks at their upcoming products.
I also get that members of the fan community usually post these images out of excitement, and as an attempt to boost their standing with peers. Heck, bloggers like me thrive on having new news and being the first to bring it to their readers!
Nevertheless, I recommend you read the letter via Brickset to see TLG's response. I'm not going to back a particular view on this issue. I do recommend that folks understand the true impact of posting these pics next time you come across them.
I have decided over the course of time not to post these types of pics here on the site. I'll also be reaching out to others in the online LEGO community to understand the impact of 'describing' future items in those photos (I did after all talk about the new Series 5 photo). Through understanding the full set of issues, it will guide the actions we take here on the site.
A possible word of warning. Note in the letter that TLG has set up a 'hotline' of sorts for people to report when they see confidential images posted on the web. There's a least one case of late where Flickr accounts were deactivated, supposedly due to the posting of said images. I'm sure blogs can be turned off or legal action taken if it comes down to that. LEGO will only 'play nice' for so long, after that it wouldn't surprise me to see them elevate their actions against leaked photos. I mean look at the kid in the bottom left corner of the memo. TLG may send him to your house for a right beating to your shins if you don't comply...