Should I build a tool to index public Facebook posts to help customers generate leads ?

I might suggest starting with Bitly and exploring the possibility of getting a custom branded shortener, which you can set up through Bitly once the domain is purchased. For example, my website is philpallen.com but I shorten all links to philp.al/link so it's more professional. I feel like many other shorteners look like spam, but I'd say your safe with Bitly because it's widely used. A custom one would be even better!

There are different ways that you can make a profit from a Facebook group. The key is to understand your audience and know what type of services/products they would be interested in. You can charge businesses or companies that are looking to target that specific audience a flat fee and post their products/services on their behalf. You can add affiliate links for products or services that are relevant to your audience and earn commissions on the sales/leads generated from those links. You can sell advertising on a CPC basis. Etc...

Of course and have in the past.. With FB's Open graph search you can laser target buyers and weed out tire kickers.. This is a no brainer :)

I don't know if you have tried this yet, but sometimes having a lookalike custom audience that is 99% similar doesn't always preform better than the lookalike audience that is 97% similar. If I were you I would go through AB test each of the different lookalike audiences, so try 99% vs 98% vs 97% vs 96% vs 95% and see if the less similar audiences will still give you good results, because they should also have a larger audience group for you to market towards. Also have you AB tested interest groups? I'm not sure what your exact niche is but i've worked on campaigns where certain interest groups preformed better than the lookalike audiences. If you're spending a decent amount of money on Facebook ads, having a professional go through and AB test your ads can be a very good idea. It's the difference between having a good ad & knowing you have a perfect ad.

I've been in the picture messaging space for a while now with my apps Lutebox (voted one of London's top ten most loved apps) and now Click Messenger. I've written a few articles about the space including a recent post about the Future of Mobile Messaging. Snapchat started out as an app called Picaboo, which pretty much did what it does now (prior to the latest update with chat and video calling). They quickly rebranded but saw a little uptake in user numbers and had quite low downloads for several months. Then around Christmas 2011 one of the founders' mom had told her friend about the app, who told her kid and her kid basically then spread the word throughout their high school in L.A. That was what really blew up their download numbers as it spread across teenagers at local high schools. As far as I know they didn't advertise in the early days, relied solely on word of mouth. Also it is assumed that they have a solid user base. Comparatively speaking, their user base may be in the low tens of millions, which may a great base of users, but nowhere even close to being as big as Facebook or Twitter. I'd be happy to speak about this in more detail or about the picture messaging landscape and what I believe to be the future of mobile messaging.