Between you and God.

I've seen people asking their ustaz or ustazah on certain issues of doubt, hoping for some positive answer and then I guess they are thinking.. 'Yes! Ustaz says OK! - so that means boleh buat.. tak dosa. '

An example: Can I jamak solat zohor and asar, because my working hours doesn't permit me to do asar? So the ustaz answers, if the situation is that difficult for you - for you have no way out and you're afraid that you'll miss the asar prayer, then it's ok to jamak the asar to zohor.
(This is based on hadith the opinions from among the 4 well known imam mazhab)
So this fella goes away thinking.. ok I can do that - tak salah, tak dosa.

Fine, if it is really so. But don't forget, Innamal a'malu binniyaat - actions are (judged) by the intentions, not on what the ustaz tells you.

The ustaz was providing the hukum, based on the little and vague information provided to him. Finally orang tu sendiri yang paling tahu, if it is ok to do this or not, based on the arguments provided. For only he knows if he has tried or done enough. Or if he is just taking things for granted, taking the easy way out.

Yea, I'm sure he knows.

According to Wabisah bin Ma'bad (r.a.) who said, " I came to the Messenger of Allah SAW, who said, 'You have come to ask about righteousness?' 'Yes, ' I answered. He said, 'Ask your own heart for a fatwa. Righteouness is when the soul feels peace and the heart feels peace, and sin is what creates restlessness in the soul, and rumbles in the bosom, even though people give their opinion (in your favour) and continue to do so.'
~ narrated according to the two Musnads, that of Ahmad bin Hanbal and that of al-Darimi, with excellent isnads.
- from Imam Nawawi's Collection of 40 Hadith.

Kalau orang Melayu cakap apa tu... 'tepuk dada, tanya selera'?

Allah is Most Wise.