But maybe you have a complex treaty that forbids spying? Or maybe you just use the info to extrapolate exactly what tech level your opponent has? I myself would at the very minimum use the info to make some pompous rhetoric about how the backstabbing duplicitous
playernation had been caught attempting to steal our glorious tech - and use it as levarage in any subsequent negotiations
The point is that the information can only be useful, if we got popups in pbem like you do in solo we wouldn't complain about getting the information would we? And Aggie is right - spying without having to report a failed mission is risk-free, and obviously dosen't work as intended from a design point of view... I like the spying part of the game a lot (mwuhahaha) but it only really works from a game mechanics aspect if you can get caught spying, which means reporting the stuff firaxis failed to implement in multiplayer.