Can you cross Central American borders unofficially?

[FrancisTapon]

Someone asked me (and accidentally deleted his post) if it's possible to sneak across Central American (e.g., Guatamala) borders without later running into trouble when you try to leave the country.

I'm sure that officially doing this is against the rules. However, it's not clear how well they enforce these rules. For example, I wrote about sneaking across the Mexico-Guatemala border and I had no problems down the road.

On the other hand, when I switched passports when I traveled from Costa Rica to Panama, Panama gave me problems. The Costa Rican government stamped my exit, and Panama wanted to see it on the same passport that I was using to enter Panama. I was trying to use my EU passport instead of my USA one, but this screwed up their paperwork.

Whether you backpack or kayak across the border, it's best to be official. However, Latin America is pretty easy going, especially with Americans, so I would probably be lazy, take a risk, and then deal with the hassle (if any) later. However, I often take risks that others don't like.

My best guess is that there's a 30% chance that there is a problem sneaking across the border, but I'm no expert. Tell me how it goes!