It's true it may be more fun to hold, but not always the best investment because of the high premiums.
I have some SIVR, SLV, SLW and even some AG. I sure hope silver goes up in the next 4 years, because it's now a big part of my retirement.
There are checks and balances and audits and what not since they are traded on various financial exchanges. I wouldn't be too concerned about a full on long term scam, but someone deciding to take the money (or bullion) and run is always a possibility. Bankruptcy is also a possibility, as was the case in the MF Global example. In the event of a bankruptcy, just remember the order in which people get paid: Lawyers, secured creditors, unsecured creditors, preferred shareholders, shareholders. I may be mistaken, but I believe people who own shares in the PM companies are considered shareholders.