Generally, with enough effort, it's possible to cheat anything and every input to prevent that is of course very valuable, so thanks @erkan for bringing this up.

However, let's set aside the technical aspect for a moment and look at this solely through cost-benefit. We can spend some GRC on this from the Foundation to attract newbies, provide them with a quick 'first payment' and create some positive promotion for Gridcoin in the end ('the most advanced faucet' etc). That objective is worthy and benefitial even if we are cheated of some GRC in the process, simply because in this case pros outweigh the cons (at least in my opinion).

Consider an analogous example - our advertising with Google AdWords. We spend 5 USD every day on AdWords and it's certainly possible that individuals who don't like Gridcoin click our ads simply to incur us more costs, since we have to pay for every single click. In other words, such individuals are cheating on us (in a way). Of course, Google has mechanisms to prevent such cheating on a massive scale, but it's certainly impossible to stop every malicious individual. Coincidentally, every such malicious click is costing us about 14 cents on average, which is roughly equal to 20 GRC (i.e. same as the 'researcher's bounty' offered through this faucet). Shall we completely stop with advertising because of this? No, because pros of advertising outweigh the cons. No risk, no gain.