The internet has greatly reduced the effort it takes to obtain collectible coins.
While every coin collector should be obtaining coins from searching their pocket change on a daily basis, and from bank and mint produced rolls, the internet will offer high quality coins that will probably never be found in circulation.
Online coin collecting is not for the new collector as there needs to be a fairly high level of coin knowledge needed to assure a fair deal and to be confident in not being scammed.
There are different types of coin sales on the internet ranging from formal numismatic sites to individuals advertising coins for sale on a self made free Word Press blog.
All of these have their plus and minus.
The biggest problem outside of outright theft is in coin grading.
There is a scientific method for grading coins but even among two honest collectors there is enough subjectivity for major problems to arise.
If you are buying coins online there needs to be a money limit above which you will demand a professional grading and evaluation.
This will cost money but you are dealing with high quality, high price coins and it will save you money in the long run by having properly graded coins.
Less chance of scams or badly graded coins will happen with the formal numismatic auction sites.
You can find these sites online at Coin World online or the printed version of Coin World.
The minus side of professional sites is you will likely never get a "great deal" like you might on a personal site.
The professional numismatic site will always be at retail or above retail.
There are totally beautiful coins that will add great value and great enjoyment to your collection.
Just realize it is the World Wide Web.
Both the good parts and the bad parts.