Mobile Advertising

Quick question really regarding mobile advertising and best way to monetize.

Do people think it’s worth having a mobile designed website with specific ads, or just having a design friendly ad which looks OK in the mobile browser and displays the standard advertisements.

This is a great question. And, although I do not consider myself quite qualified to answer it I want to share something important to consider.
My first thought is that the ‘audience’ (or demographic) that visits the site using a mobile device is most likely different than that which uses a desktop browser.
Granted, there is an overlap of user-type who visit with a desktop browser, but you can be sure the mobile visitor is more mobile (aka active) and probably a bit more tech-savvy. So, I would venture to say your advertisers may be interested in reaching those [a bit] more targeted audiences in a different way.
At the very least, take into consideration that the mobile user who visits the site is NOT using a screen reader and less likely to fill out a lengthy form, due to the form of the device.

If you want to have a high conversion rate, you will be best off using specific ads for each screen size.

I vote for a mobile designed website with specific ads, but first check how your website works on a number of mobile devices: smartphones and tablets running various platforms. Screen size is a crucial issue in any branch of mobile development and it influences user experience a lot.