Jun 28, 2011 08:04 GMT  ·  By

There's been a surge in online payment services lately, especially, almost exclusively, on the mobile front. But this doesn't mean that the old guard is going anywhere any time soon, the old guard in this case being PayPal which has just reached the 100 million active users milestone.

PayPal has confirmed the figure, according to TechCrunch, but has provided no other details. It's also unclear what PayPal counts as active users.

Still, it's a very impressive figure for an online payments solution so it's no wonder that PayPal now makes up a huge chunk of eBay's revenue and profits, starting to overshadow the main eBay site.

PayPal brought in almost $1 billion in revenue in the first quarter of 2011 alone, a 23 percent growth year over year.

The company's Marketplaces unit, basically the auctions site, brought in $1.5 billion in the same period of time.

Despite the growing competition, PayPal seems to be doing alright, even if it may be out of pure inertia. Still, there don't seem to be any real challengers, startups like Square or big pushes like Google's Wallet look great on paper, but have yet to make any significant impact in the real world.

And PayPal itself is moving boldly into mobile payments. Recently, it increased the expected mobile transactions volume, doubling its initial estimates.

PayPal now expects to see $3 billion in mobile transactions in 2011. The service is already seeing about $10 million per day. At the end of 2010, it provided guidance, estimating $1.5 billion in transactions.

"We first predicted $1.5 billion in 2011 mobile payments volume. At our analyst day in February, we upped that to $2 billion and just a few months later, we have now added another billion to that number," PayPal said in a blog post last week.