I've never visited Pompeii, but if it is like some other historical sites I have visited, they were suffering from lack of care and maintenance too...
One I particularly remember was Napoleon's villa at San Martino on the island of Elba... The last time I was there - in 2003 and it was pitifully run down.
However when I was searching for this little picture I noticed an entry about the 'restoration' of Napoleons Villa on Elba. I must admit that it now seems worht a visit - some of the work seems almost a miracle! If you've never been to Elba, try and add it to one of your visits - it is my favourite place in Italy after the Alps!!!