This may be "Ol news" to everyone here, but this isthe first tme I've been to this PPC Thread within SEO Chat, and I thought this was an important piece of info.

I do not participate in adwords, but will be very shortly.

This kinda seems like old-hat SEO info to me because I know what changing a URL can mean, but again I thought I'd add this:

Changing the target URLs of your ads within your AdWords campaigns can really take a toll on your earned rankings within AdWords. As we all know, Google uses a ranking algorithm within its paid listing program which looks at both CPC and CTR, when determining rank. Ads over time can outrank other ads even though they are paying a lower CPC, if they have a higher CTR. By changing the ad (I think in any way - although I am a newbie with AdWords management) the CTR history is wiped out. By losing that CTR history, you can dramatically affect your ad’s ranking. In a WebmasterWorld thread named Google Adwords destroyed my account a member tells us a story;

A couple of days ago, I decided to update my adgroup ads in a campaign that I have run for many months. I had excellent ranking in all of them, some I was #1 and #2 in the blue area for many. I made a domain name change to all the ads in this campaign (about 30 adgroups). When I checked later to see how the ads looked and their position, I could not believe my eyes. Every single keyword that I had worked so hard and spent thousands to get in a great rank and reasonable prices was GONE! It was as if I had started over as a new member. The worst one was one where I was #2 in the blue and ended up as #38 on the fourth page! Paniking, I called google and emailed them. The tech person that I talked to there said this is the worst he has ever seen of destruction of rank. Later on they said that part of the quality part of an ad is its domain name. Then they said the new ad had to get some quality thru I guess getting impressions and clicks. Well I told this gentleman, “how am I going to get quality in the 38th position?” I am getting the run around at google right now. They are not admitting that the system is flawed. There was no warning, nothing written in the literature that this kind of massive destruction of an account could happen.

I feel bad for this member, but others in the thread to not feel as bad as I. One member says that “It is “public knowledge” that a change to URL will get you to loose your history.” And then he offers advice, “The better way to go would have been to add a new ad with the new URL, then waiting until it gets the same CTR and position than the old one and then deactivating the old one.” Others try to make the member feel that he/she has other options. The member can use the API to try “reinstating your old ads” or try calling Google to do so. But in this specific case, it won’t work. Others say that in time, the ads will navigate its way to the top.