Smartwater contains a chemical code which is unique to you as a purchaser. It's reckoned to be "virtually invisible" to the naked eye - if that's vitually invisibe as in the VERY visible marker pens that the police tried to get us to use - then I wouldn't want it anywhere near my vinyl.
Cross-contamination would be an issue too, especially if you dj. There's a possibility that the chemical marker would be tranferred to the decks and anyone else handling your vinyl, to anyone using those "contaminated" decks and to any other vinyl played on them, etc, etc, etc.
I reckon your answer lies in good security rather than a marking system.
Good luck,
- Kev