To add to your point on bribery, let's not forget that many countries have laws against bribing foreign officials. In the US it's the Foreign Corrupt Practices Act (http://en.wikipedia.org/wiki/Foreign_Corrupt_Practices_Act). I'd assume Europe has something similar (Wikipedia brings up a missing link to a European "Criminal Law Convention on Corruption", but I haven't looked into it).

Even if the host country is somewhat lax in its own enforcement, laws like this could make returning home rather dicey should one find themselves paying "unofficial costs".