||I'm going to assume that you live in the United States. If so, it's not particularly safe to order seeds in any manner. It's a violation of state and federal laws to purchase or possess Cannabis seeds and if they catch you could certainly charge you with possession of a controlled substance. I can't think of any particular reason why ordering online is any more or less safe than ordering by phone or through a catalog by mail...the following issues apply to all these methods.|
Part of the issues is how a particular seed company packages their seeds. If it comes with a large "Cannabis Seeds" label on the package, the risk of being caught is significantly higher than if a company packages discretely. The primary issue, however, is that there are no companies that sell Cannabis seeds from within the United States, so packages must pass through customs. Customs has the right to open any package they wish as it enters the country.
If for whatever reason, customs decides to open the package, they have a number of options. The first and most likely is that they will remove the seeds and forward the empty package to you with a note enclosed saying that a scheduled substance was confiscated. While this happens to many people with no additional followup from either customs or law enforcement, it's quite certain that your name would now be on a list somewhere. Another possibility is that the seeds could be turned over to federal or local law enforcement and charges could be pressed for possession of a schedule I substance. Obviously this is not something you want to deal with.
Some people choose to minimize the risks by having seeds shipped to a friend in another country who then repackages the seeds for shipment into the U.S. The theory is that customs is less likely to open a person-to-person package from Canada (for example) than a package from a company in Amsterdam.
Lastly, is the paranoid possibility...while your seeds might arrive on-time with no problem in your mailbox, the possibility exists that customs did indeed catch them on the way through but has chosen to forward them along with the intention of allowing you to grow full-sized cannabis plants before paying you a visit at your home. While the chances of this are pretty slim, it can definitely be an uncomfortable thought in the back of the mind.
We don't have any hard numbers on this, but would guess that most seeds ordered into the U.S. arrive with no problem. But the possible down-sides are pretty high.