Ancestral links reliability from DNA test

[Glen in Tinsel Kni]

As others have said the dna and the trees may not tally, I'm adopted, both my parents are NPE's as is one grandmother so I have lots of mystery matches.
Granted my matches are probably somewhat closer but I have 3 matches of 150-185cM all born during WWII and registered as illegitimate in Sheffield, they deny any link to me or the others and have trees that don't show any mutual connections yet we all share dna with each other. 

[Glen in Tinsel Kni]

As far as those trees with thousands of illustrious ancestors (I have one with Alfred the Great!), call me a sceptic...

Only one! Pull you socks up man, you should have dozens like me 

[Norfolk Nan]

     I might have, it's the one I saw yesterday so remembered it.