Here in Norway they've tried to curb this somewhat by eliminating the wealth tax value discount you get on secondary homes. Your primary gets a 75% discount up to $1mill, then 30% on anything above $1mill, while secondaries count in full. So it's much less favorable to own multiple homes now as an investment.

Of course, most of those who did own extra homes as an investment rented them out as well, so rental prices here has gone through the roof as landlords and common folk with an extra apartment or two has sold the homes.