Firstly Service Providers use BGP extensively for route propagating.
In addition some MPLS SPs mandate using BGP to connect to their MPLS networks so as a company you may have no choice but to use it.
But the above aside then I guess the question is why would you want to use it as a company specifically in relation to internet access.
The answer is that is a big question to answer and there are many variations on why and how could be useful, too many for one post really.
To try and keep it simple if you had just a single connection to an ISP then BGP gives you pretty much nothing because BGPs primary purpose is to enable you to influence the path traffic takes and you only have one path so it makes no difference.
If you had multiple connections to your ISP(s) then BGP might be applicable. I say might because even here it depends entirely on what you are trying to achieve in terms of link usage eg. if all traffic is to use the primary link and only use the backup link if the primary fails then again BGP might not give you anything here.
And even if you wanted to use both links equally then BGP might still not be the best choice because two default routes would do just as well.
Bear in mind that for a lot of companies BGP is not really a choice ie. they are assigned a small public IP range from their ISP and no dynamic routing protocol is used between the company and the ISP.
Where you do need BGP though are in two specific cases -
1) where you have your own provider independent addressing and your own ASN in which case it is up to you to advertise that addressing to your SP ie. you are in effect responsible for advertising your public IPs to the internet
2) when you do want to influence the path traffic takes across multiple links based on network prefixes and BGP gives you a lot of flexibility in doing this.
The final point to make is the amount of routes you need to receive if you are running BGP.
Again there are a number of different options here ie. just defaults although this gives you very little control over which path to take if you have multiple active links, a subset of the full internet routing tables or full routes.
It all comes down to what you are trying to achieve and what connections you have.
All my experience of BGP has come because our SP mandated it for connecting to their MPLS network and as we had multiple sites backing each other up this meant i needed to understand the ways to manipulate traffic in BGP.
If you have no need for it in your company but want to get familiar with it I suggest running GNS3 on a PC/laptop and playing around with it there.
Jon
