URL Shortner Service - how to monetize?

In the world of microblogging where users are trying say more with less, it is important that the resource url do not take more than the actual message. Enter the "URL Shortner Services" such as Bit.ly, is.gd, TinyURL among others, to the rescue to shortened those long URLs. From a user point of view, this is not much life to shortener services once the url has been turned to a small set of characters. I personally do not believe that anybody uses url shorteners outside the microblogging realms. We all know that there is no such thing as a free service, especially if you are looking for the service to stick around for a while. Therefore one question comes to mind, how can we make monetize the service.

I was at bar in Canary wharf with one of my investment friend when we were discussing several monetization ideas in regard to social networking based businesses. Obviously, Twitter was discussed but then the conversation shifted toward the third party apps built for Twitter and microblogging sites.

I am sure that anybody using Twitter has come across those funny urls in twits. When you clicked a link, there is a redirection from the url hosting server to the original source. So how can we monetize this service? That same question again. Here are some ideas and you are welcome to agree or disagree.

1. charge microblogging site and third party developer to use the service and implement a free quota. I do not personally see how this is going to work as the microblogging site are currently in the driving seats. This option might not be viable for the url shortener service providers.
2. when a shortened url has been clicked, the hosting server should redirect them to their site and present the user with an advertisement which will be displayed for a few second or until the user clicks it off. The ads have to be targeted the user this might involve parsing the title of the original source for keywords. This solution might be a good approach but how will user react to this. It can put them off therefore the services might have to offer some incentives to the url referrer.
3. This probably the simplest way and less intrusive from a user's perspective. When a user clicks on a link, the original site should be opened into a frame which is integrated into url shortener service provider's site. The top frame of the window could display some ads.

The above are just some suggestions and they might not even be feasible or might be receive with hostility from the community but it is worth trying. Here is my final option:

• Twitter should implement is own url shortener service where the destination page will be displayed within a frame simialr to option 3 above. Or twitter should open all links within a frame and advertise similar to option 3 but this time without cutting out the the third party url shortener service providers.

That's all folks!