Paul La Monica, over at Business 2.0 is urging caution and some prudence when it comes to investing in VoIP stocks. I don’t necessarily disagree with his thesis. La Monica, a colleague from the old Red Herring days quotes Victor Schnee, president of Probe Financial Associates, an independent telecom research firm, who says that the investors have to focus on how much it is costing these smaller players to sign up customers. “There’s an issue as to whether profit margins will be sustainable,” said Schnee. “Marketing costs are going to be very high and this is going to be a very competitive business,” said Schnee.