I dont think i protest too much - i have always hated lies of any kind.
The situation where you say about a gift is very different and i dont think anyone would go out of their and cause the pain for a lovely surprise actually.
But if my h spent huge amounts of money we did not have on a gift then yes i would be very cross.
I am by no means perfect and i do 'forget' the price of things i have bought but it is a very different lie to actually allowing your partner to think they are going mad in some way which is often the case during affairs.
All lies serve a purpose - some are lovely such as gifts, some are to save hassle and some are to actually hurt the other person.
Children naturally lie and learn very early that it can keep them out of trouble.
When my h had his affair i dont think he went out of his way to destroy my trust (even though he knew deep down it would do that) - he lied to make HIS life easier - at that time he was not thinking about anyone else or how they really felt in all this.
And as for the trust thing - well i pity the poor salesman now who tries to 'convince' me of anything.
I do not trust easily and have a few good friends rather than a lot.