So how about DomainTools then?
I don't have any evidence for them doing anything but they are a domainers tools

I'd use them for what they are good at - looking at someone's whois. I wouldn't use them to determine availability.
I often use instantdomainsearch.com (or similar) figuring that if you're typing one letter at a time it's really hard to know what you're actually checking (not that anyone cares).
I usually just go to Dynadot/Name (who I don't think steal anything) and just search for a different extension (or without extension). If you want:
CLOUDCOMPUTING.CO.UK
Put into the check
CLOUDCOMPUTING.US
It tells you which other TLDs are available.
Does it work? Frankly, I don't think most registrars are busy filtering through 100,000s of queries to make registrations. Chances of getting enough regfee domains to make money on without being an active domainer? Near Zero.
Best thing imho is to just run an internic.net or verisign whois script from your server for .com/.net and for anything else use the above method.
I think what happens in reality is as was alluded to earlier. A couple of registrars "hold for their customers" which is BS but they are the places most of us don't use.
Somewhere like Name.com that is heavily into tooling and analysis is likely pulling the information and using it to feed their "suggestions". Somewhere like GoDaddy.com often presents names similar to those you currently have and suggestions so may do similar.
I think most of it is just people registering the same name. A lot of domainers will search google for inspiration. If you imagine 1000s of domainers searching for "What happens after cloud trend?" you will likely have them all looking through the same few pages for inspiration and being inspired by the same thing.
Also - most names you pick up have been registered before and are not as "fresh" as you think. New names have footprints everywhere.. so your original idea may have been three other original ideas previously!
So - you're not the only one looking. About 99% of new regges are dropped. If you had to think about it too long you just saved $8 is how I look at it
//Apologies for the rambling discombobulated post. Doing too any things at once.