If your target group is companies you may skip all protection systems. Fair usage conditions, like mentioned above, are a must have. But, it's a good idea to add something that is annoying to circumvent every time if you wanna use it illegally. If your product creates files, add copyright hints to it, that are gone with the license key, but need hands-on work for illegal users every time they use your software.
If you think about protection systems, use the strongest, with the best update frequency, and the most individual configuration (personalization of code sections) you can get. Crackers need only days to produce a hack (or key generator) of the simple protection systems. With the last review I did in this arena I preferred Software Passport (maybe two years ago):http://www.siliconrealms.com/
They are part of Digital River (e.g. RegNow, ShareIt). So, you can use this technology to let create a key on the fly when customers by at RegNow, ShareIt, etc. Pretty straight forward.
Service as add-on to register is a nice idea. But, not interesting in Shareware. Why you buy Shareware? Mostly, because of the limited price you've to pay for it. Service is something for the big software sellers, with complicated software products.