Finding people with email lists

Many of us here know how to find people with email lists in our niche by searching NICHE NAME "powered by aweber". The question I have is: is there a better way do this?

My thoughts:

1. Not everyone uses aweber, so the strategy above automatically limits the results.

2. I'm assuming that people with legit squeeze pages that don't have "powered by aweber" anywhere on their page (see mattmason.info/squeeze for an example) are going to have larger lists. I am making this assumption based on the fact that they seem to know what they're doing a little better than people who just insert the autoresponder code into a template. The professional squeeze page is a more professional approach IMHO. (I'm not knocking anyone here, just saying that some people take it to the next level.) Also, from what I've seen when doing the "powered by aweber" search, most of the results have me literally searching the webpage for the opt-in form. These people don't seem to understand the eye path of a user. (See http://www.digitalmarketer.com/acces...-squeeze-page/ for an AWESOME video on squeeze pages.)

Those two things being said, does anyone know a better way to find people with lists than by doing the search that I bolded at the top of the post?