The person, company, or organization whose name it is gets to decide, within limits, how the name should be written:

My parents bought the iPad on eBay.

However, when you begin a sentence with a name that starts with a lowercase letter, capitalize the letter, to mark the beginning of the sentence:

EBay sells all kinds of things.

If an organization or a product spells its name in all caps — or in all lowercase letters — do not follow that style unless you are writing advertising copy or unless the name is an acronym (such as IBM).

My VISA card was declined, so I ended up spending the evening at home alone, on reddit.

Capitalize just the initial letter of the names:

My Visa card was declined, so I ended up spending the evening at home alone, on Reddit.