Payment channel networks (PCN) have been introduced to solve scalability problem of permissionless blockchains such as Bitcoin. The Lightning Network (LN), launched in 2018, is the most prominent PCN built on top of Bitcoin. As of March 2020, LN consists of over 11 thousand nodes and 36 thousand channels, collectively holding nearly 900 bitcoins (7.8M USD).A payment channel allows two parties to lock funds in a multisignature address and then modify the distribution of funds in nearly instant transactions, without confirming them in the blockchain. As LN transactions are not broadcast and not publicly stored, LN has been seen not only as scalability but also as privacy solution. The protocol guarantees that only the latest channel state can be confirmed on channel closure. LN also supports multi-hop payments, where the balances of multiple channels along a path are moved. The atomicity of this process is guaranteed by hash time-locked contracts (HTLC). LN nodes gossip about channels available for routing and their total capacities. To issue a (multi-hop) payment, the sender creates a route based on its local knowledge of the graph. As local channel balances are not public, payments often fail due to insufficient balance at an intermediary hop. In that case, the payment is attempted along multiple routes until it succeeds. This constitutes a privacy-efficiency tradeoff: hidden balances improve privacy but hinder routing efficiency.In this work, we show that an attacker can easily discover channel balances using probing. This takes under a minute per channel and requires moderate capital commitment and no expenditures (the attacker's funds are only temporarily locked). We describe the algorithm and test our proofof-concept implementation on Bitcoin's testnet. We argue that LN's balance between privacy and routing efficiency is suboptimal: channel balances are neither well protected nor utilized.We outline two ways for LN to evolve in respect to this issue. To emphasize privacy, we propose a modification of error handling that hides details of the erring channel from the sending node. This would break our probing technique but make routing failures more common, as the sender would not know which channel from the attempted route has failed. To improve efficiency, we propose a new API call that would let the sender query balances of channels that it is not a party of. We argue that combining these approaches can help LN take the best of both worlds: hide private data when feasible, and utilize public data for higher routing efficiency.