This article today on LewRockwell.com gives some good arguments on buying silver. The first good news about this piece is that he did not constantly talk about how there is a supply shortage of silver and that it won't be able to keep up with increasing demand. Those arguments have been going for decades and they are useless.
This article talks about the gold to silver ratio. The author says that the ratio is unusually high and that it has been typically much lower in the past. This is an interesting statistic to look at and keep an eye on, but at the same time, past results don't necessarily indicate future trends.
Silver is the poor man's gold. There is nothing wrong with buying silver. It is easier to buy a silver coin every week than buy a gold coin every week unless you happen to be wealthy. With stocks and ETFs, it makes no difference.
Personally, I prefer gold to silver because gold is perceived to have monetary characteristics more so than silver. Gold is also much less volatile. Of course, if we have a bull market in metals, silver could easily outperform gold by huge percentages.
I recommend that you have both, but you should have far more gold and gold related investments. If you have 20% of your portfolio in gold, then 5% of your portfolio in silver would be good. In other words, I recommend you have about an 80/20 split in favor of gold. If the metals go down, you won't take as big of a hit with gold. If they go up, at least you will have a small portion in silver to benefit from the huge gains.