It's not just mappers, specialists are exactly the same.
Biggest issue i have is i've seen dozens of people find out the hardway why you need a decent mapper. I've been around subarus for heading towards 15 years now and seen mappers and tuners come and go. I've been lucky enough to know and talk to alot of the more well known subaru owners with some of the big track/race cars.
It also seems to you can't have an open discussion about things on forums, either for legal reason or it becomes a slagging match or if on facebook people just get banned when they put up the other side of the story, let me give you an example.
After market ECU's, there a ball ache to setup to run like OEM, cold start and idle are particular areas that take alot of work, cold start is the worst because once the car is started in the morning you have to leave it over night again for the.
Car came into a tuner running crap, idle was a mess, cold start was crap and yes you guessed it was running an aftermarket ecu. Was a Motec M800, not bad for about £3000 at the time. Car was a 03 plate sti had decat, panel filter and motec, nothing else. He wanted it running better and more usable as a daily car.
Motec M800 is a race spec ECU and simply put was massively OTT and not needed for the spec (given the OEM drivability affects) so the customer was recommended to replace the Motec with a standard ecu and ecutek map, sell on the motec and fund the rest of the work that way.
So thats what they did and walked away with a car they loved driving again, mega happy with the car and £100 in their pocket in money they got for selling the motec on to dave roe.
Fast forward 2 years and they sell the car on with a wedge of receipts for work done etc etc. The receipt for the removal of the Motec is spotted by one of these pop up 'specialists' the new owner takes it to and of course without knowing exactly what and why it was done they start making accusations of ripping people off etc etc. when the reality is very very different. That one was on Facebook.
The issue i have with Open source is it is not only ripped off ecutek software from the US but it has also allowed anyone to set-up and map away whether technically competent or not. Typically these mappers learn to map at the expense of the customer, local company was setup near me they mapped 20 cars we know of, 7 blew up during mapping and the customers got zero compensation, 3 of the 7 were forced to sell their cars due to not being able to afford the repairs.
The final point to note is alot of these type of mappers do road mapping, they have no insurance and no tech backup. The customer is happily driving along thinking they are insured by their own insurance when in reality they aren't, if the police pull them over on one of the high speed pulls they will be prosecuted for driving with no insurance etc etc or od forbid they had a crash there own insurance would reject their claim and report them for driving without insurance.
I get alot of stick for supporting Scoobyclinic, but when ever i hear something i tend to go an ask whats cracked off, 99% of the time it turns out not to be as stated and either customer didn't like the responce they got (how to you tell someone their headgasket has gone without upsetting them?) or faults have been found that need sorting so bill is larger than expecting (so if customer says he wants a new roll bar and gets a price for that but they find drop link bush has gone should they ask if the customer wants the bush done on the drop links or leave them with a duff bush?).