1v1 100%, I think it's not a big deal.
The problem is this. One side starts spamming snipers, now you're 2v1 or 3v1. Good luck. You CS, only to get CS back instantly.
There is also upkeep. Upkeep can be increased to allow for say, 2 snipers max, before it cripples you too much. By going upkeep, it does not eliminate the tactic entirely, but it comes at a heavy cost to your economy. If those tow snipers don't perform as intended, then you are behind by A LOT.
I do not like negative zeal on snipers, because the original concept was designed around piospam with flamers, which are close ranged units. Snipers can be far away from each other and not much of their efficiency will decrease (albeit, it requires more skill to manage them properly)