Use to cross the Blaine border every night for 2 years. They are dicks and always have been. They threatened to do a body cavity search on me once and I told him he'd better callin for some more backup.
They have device that they can plug into your cellphone and download everything on your phone, laptop or any other electronic device you have. The Patriot Act made that unconstitutionally legal for them to do. If for some reason they want to charge you with something they can use that in federal court against you. If its done through a state court that evidence CAN NOT be used against you because it was gotten without a judge signed search warrant. Pictures on cellphones can be traced right back to exactly what camera took the picture and if on a cellphone it embeds the GPS location that picture was taken. Its called IPTC data.
Never use a cellphone for cannabis. Turn the celpphone off and remove the battery before you go to do your business. When you're done put the battery back in the cellphone and turn it on. I don't mean to get over paranoid here but they can also legally put a small transponder on your car and know exactly where you are going and where you've been. Its already been done quite a few times. The chances they did that to you are propably pretty slim but it still might be a good idea to take a good look around and under your car.
The border patrol generally isn't worried about small time potheads but if they suspect you're involved in transporting any kind of quantity and they'll take a closer look at you.
Getting into trouble at the border was almost a nightly thing for me when I was crossing. I was never doing anything illegal so I just held my ground.