Paying for Inclusion in the Search Engines and Directories: PFI, PFP, PPC and Trusted Feed

It seems that everywhere we turn these days in the search engine marketing world, we are constantly hearing the phrases pay-for-inclusion (PFI), pay-for-performance (PFP) and pay-per-click (PPC). Here is a quick primer to explain what each of those programs means.
Pay-for-Inclusion
For the past few years, many of the search engines (except Google) have offered a simple PFI model so you could speed up the indexing of any page of your site by paying a fee. This fee covered a year of inclusion in the search engine database plus frequent respidering of the page, if it met with the engines' quality requirements.
Many human-edited directories have also offered PFI programs in order to list your site.  

For instance, if you have a business or any type of commercial site, you have to pay Yahoo $299 for them to consider your site for inclusion in their directory. Once reviewed by their editors, if they believe your site is up to snuff, they'll then add it to the directory, and you simply have to pay a yearly fee to keep it there.
My personal feeling is that a Yahoo directory listing is not as beneficial as it used to be, however. In fact, we've had many forum discussions about this. For more info, please read this discussion at the High Rankings Forum.
Pay-per-Click
The search engines also offer PPC programs where you purchase ads that show up at the top, side or below the search results for the specific keyword phrases you bid on. Google Adwords and Overture are the best known of these programs. Ads that you place with these companies show up at the search engines as well as many content sites (if that option is turned on). Generally they are labeled as "sponsored" or "featured" results.
In March 2004, Yahoo announced their new Overture Site Match(tm) program that combines PFI with PPC. They still offer their traditional PPC sponsor ad program, but they no longer offer a simple PFI program. Now, if you want to speed up your inclusion in Yahoo and its search properties and partners (currently AltaVista, FAST, Yahoo and some of MSN), you'll have to pay a fee for each URL that you want included, PLUS 15 or 30 cents (depending on your category) for every clickthrough to your site.
There are three important things to note about this program:
1) The money you spend goes solely towards placing your site into the search databases, and enabling 48-hour respidering of your page content. You can pay them all you want, but this program is not going to give you a higher ranking, so keep that in mind.
2) It's *not* actually necessary to pay to be listed. Yahoo is not removing pages that aren't paid for, and they continue to add new pages for free. Their spider (Slurp) is constantly on the crawl for new information, and new pages are in fact getting added fairly quickly these days - again, for free.
3) If your site has been around for a while and other sites are linking to it, chances are that your pages are already included in their database for free. Beware of paying for what you already have, and then paying for every click thereafter.
You can check whether your pages are already included in Yahoo's database by going to Yahoo and typing into their search box the following command:
site:www.yoursite.com (be sure not to leave a space after the colon in site:www).
When you see the list of results, find the one that has a link that says "More pages from this site" and then click on that link. That should give you a general idea of how many pages of your site are already indexed. If it appears that they've got most or all of your pages, then you're all set -- no need to pay!
Trusted XML Feeds
One additional way to pay Yahoo to include your pages across their search network is called "trusted XML feeds" (sometimes just "trusted feed," or "XML data feeds").
This service is generally reserved for very large, dynamically generated ecommerce sites that add or change products frequently. With trusted feed, you don't have to pay a submission fee for each page you want to include, just a pay-per-click fee. The benefit of trusted feed is that many of the Yahoo/Overture feed partners will actually optimize your XML feeds for you. I've worked with PositionTech for one of my large clients, and they provide this service at no extra cost. Also, you can turn off your feeds at any time if they don't appear to be providing you with a positive ROI, so be sure to track your clicks and conversions to make sure you're not just throwing your money down the drain.
My personal opinion on paying to play is that for most sites, paid inclusion is not something it is necessary to sign up for. However, I do believe there are many benefits to running PPC ad campaigns. If there are certain keyword phrases you're having trouble ranking highly with in the regular search results, a PPC campaign is a great way to maintain your site's exposure. PPC also comes in handy as a way to gauge interest in your site, as well as its products and services. It also makes a nice tool for judging which keyword phrases people are typing into the engines, as well as which ones do a better job converting your visitors into buyers.
So I give a thumbs-down to paid-inclusion (with or without paying for clicks) and a thumbs-up to PPC campaigns. With a thumb squarely in the middle for XML feeds depending on your particular site needs!