Spies have nothing to do with the general decline in the game. It has everything to do with the game being by now a fairly out-dated format and being designed in an age before 24/7 smartphone internet access.
Read this post if you want, it gives a much better picture of why this, and indeed most games, go into decline:
http://www.bushtarion.com/forums/showpost.php?p=32481&postcount=19
Such a sad ending for what has been {and will be until it's eventual death} one of my favourite internet games for years.
Many other browser-based games are dead/dying
- elderages/ww2subversion/mechreign/dragonwars died out around 2 years ago, game based on individual units of which can be trained, leveled, armoured, and bought. Game decreased suddenly from ~2k to 300 after a 4-month round game, supposedly 2.5mo., due to IE version upgrade
- tiipsi.net died out 1 year ago, based on 1 unit (yourself), where you also train, level, etc. Used to have ~high 50k people world-wide, but died due to lack of any rounds, any restart to allow others to gain high rank. Older player, which is the time of start of the game, was 5 years. S/He played the whole 5-year round.
- kingsofchaos is dying, based on level of HQ, to protect and armour your troops. Used to have high ~100k, now down to 4k due to repeatedness of game system. If i remember correctly, anytime you buy weapons/armour/troops, you'd have to enter the "captcha" in order to proceed...
- gindis, on the other hand, is popularizing. Older versions of the game was crap, random numbers, now, they have upgraded their login page, of which indoubtly, caught websurfer's attention immediately.
- tribalwars/grepolis is growing also. Graphics and war system made it interesting.
may not have anything to do with this topic, but just a note of what is happening/happened. Sad how many games are dying/dead, but indoubtfully upgrading the game over time will capture people.