Selling links is against Google Guidelines

This practice is very common but doesn’t get more blatant than this email received by a client that was unsure what to do, when advertising is the reason for inclusion within a website then the link should be blocked by using the rel=”nofollow” code. Here is the email in full (with normal sarcastic comments from us):
I’m writing to include you in the news that we are now allowing advertisements from home improvement companies on our site from only £4/week. Customers who visit us are in the buying phase of the decision making process, the perfect time to present yourself to them. This is when the sales are made.
We currently get over 4800 hits [delicious webdesign – shouldn’t you be telling us how many unique visitors you are getting?] per month and this number is growing at a rate of over 23% every month, we expect to have over 10,000 hits by xmas  There is also the availability of a link from our site to yours which, because we have the highest page rank in the industry will benefit your website enormously on all search engines. Google use page rank as a tool to decide how high you are when words or phrases are searched for. A link to a high page rank site boosts you massively. An easy and cheap way to raise your profile. [delicious webdesign – yes but surely this is against Google’s webmaster guidelines]
All adverts will be 1/4 page wide and 1/4 page high on the right side of the page. We have restricted the adverts to 4 per page and only cost from £4/week per region Each company will be guaranteed exclusivity for their product in their region. This will give you national or regional exposure at an extremely affordable price. [delicious webdesign – aha yes lets sell the advert not the link !!)
Please respond to this email to indicate interest or if you need more information we will send out more details and try to reserve your chosen space.
We have really exceeded our customers expectations for what a quality product at the prices they get when listing a job on our website. List any Granite or Quartz worktop on the site and see for yourself.
Delicious Webdesign – There are no shortcuts to high rankings in Google, if you try to manipulate the system you may get short term benefit but eventually you will be penalized and then end up with a lower ranking and less visitors than before you started buying / selling links.