My intro to snakes was a baptism of fire. My first purchase was a B&G Jungle and she was the devils incarnate, there was no way she could be handled. After several months of going against "best Practice", that is handling her (and getting bitten to the point of anemia...lol) at levels that others would deem excessive. She is now an awesome 2yo that I'm happy to hand to anyone to handle. She "tolerates" people.
I also think that they pick up on peoples feelings of fear in a huge way. I say that because I just picked up female BHP from some owners that were terrified of her. The story was that the owners went to Bali for 2 weeks and when they got home she latched onto the mothers hand and wold not let go, to the point that they had her in the sink runnig water down her mouth and nose to get her to release. When I went to have a look at her she was absolutely gorgeous and around 1400 long. I asked if they minded if I got her out, they said no we'll go and get the glove. I said no I'll just she how she goes, as I reached in to grab her I could see all the family edgy and fidgeting and yes, just after I got her out she latched onto my hand. It took a couple of minutes to get her to release she then just relaxed and crawled on me like I'd owned her her whole life. Concerned, I asked my house mate and his girl not to handle her unless I was home. I figured I always wanted a BHP and even if I couldn't handle her she would be a good display and/or breeder. After a couple of days to settle down, we decided to see how she was this time round. She is an enormous pussy cat, if I (or anyone else) opens her enclosure she leans out and climbs up onto me. To me this is not tolerance when she willingly comes out. She climbs over everyone and everything and she is an incredible change to what I first picked up.
For me, I'm happy that some people get put off once they"ve been tagged by their snake and stop handling them, otherwise I wouldn't have got a 2yo, 1.4m long female BHP with her enclosure for $300 just because they wanted to get rid of a python that they couldn't or wouldn't handle.
Cheers,
Ned