Would you hire an ad agency if it promised results?

So I was hanging out on WebHostingTalk yesterday where I came across this thread - Would you advertise with a marketing agency if they guaranteed results?

The thread starter had contacted an Ad Agency which offering him guranteed results while signing a contract which was to go something like this -

CPM Campaign. {MARKETING COMPANY} to mail to 3,500,000 of its users over a period of 15-45 days until {my hosting company} is satisfied with campaign. If, after 3,500,000 mail drops, {my hosting company} is not satisfied, {MARKETING COMPANY} will exhaust its database, continuing to promote {my hosting company}, free of charge.

Here's what my response to this post was -

Lord Brar wrote:
This clause -

{MARKETING COMPANY} will exhaust its database, continuing to promote {my hosting company}, free of charge.

Doesn't sound too good to me. If they are not able to provide you the results with your initial campaign then there are two possibilities -

1. Either they will get too enthusiastic to provide you the desired results by making it a do or die situation for themselves.

or

2. They will lose their motivation and keep dragging the thing in sub-par way.

No one can tell you what way they will go.

I am not saying that assured guarantees are bad. In fact, even our agency offers assured guarantees but we give realistic guarantees after we have assessed the whole situation and the standing of the company.

Advertising is not just about plastering ads in every possible media or sending out mailing to zillions of people (legitimate mailing list, of course). Advertising is about creating a whole atmosphere where you are able to temp the other person to buy your product. It is everything you do - Your site, your checkout process, your reputation on the internet (forums and sites) and your support handling.

The thread start has still not answered my question if that Agency actually took a look at how their site works, what is its reputation and how they handle your support and sales?

So, what is your take on the subject.